parse-time-string: add a date/time parser to notmuch

Add a date/time parser to notmuch, to be used for adding date range
query support for notmuch lib later on. Add the parser to a directory
of its own to make it independent of the rest of the notmuch code
base.

Signed-off-by: Jani Nikula <jani@nikula.org>

6 files changed, 1632 insertions, 1 deletions

diff --git a/Makefile b/Makefile
index e5e2e3a3..bb9c3164 100644
--- a/Makefile
+++ b/Makefile
@@ -3,7 +3,7 @@
 all:
 
 # List all subdirectories here. Each contains its own Makefile.local
-subdirs = compat completion emacs lib man util test
+subdirs = compat completion emacs lib man parse-time-string util test
 
 # We make all targets depend on the Makefiles themselves.
 global_deps = Makefile Makefile.config Makefile.local \
diff --git a/parse-time-string/Makefile b/parse-time-string/Makefile
new file mode 100644
index 00000000..fa25832e
--- /dev/null
+++ b/parse-time-string/Makefile
@@ -0,0 +1,5 @@
+all:
+	$(MAKE) -C .. all
+
+.DEFAULT:
+	$(MAKE) -C .. $@
diff --git a/parse-time-string/Makefile.local b/parse-time-string/Makefile.local
new file mode 100644
index 00000000..53534f3e
--- /dev/null
+++ b/parse-time-string/Makefile.local
@@ -0,0 +1,12 @@
+dir := parse-time-string
+extra_cflags += -I$(srcdir)/$(dir)
+
+libparse-time-string_c_srcs := $(dir)/parse-time-string.c
+
+libparse-time-string_modules := $(libparse-time-string_c_srcs:.c=.o)
+
+$(dir)/libparse-time-string.a: $(libparse-time-string_modules)
+	$(call quiet,AR) rcs $@ $^
+
+SRCS := $(SRCS) $(libparse-time-string_c_srcs)
+CLEAN := $(CLEAN) $(libparse-time-string_modules) $(dir)/libparse-time-string.a
diff --git a/parse-time-string/README b/parse-time-string/README
new file mode 100644
index 00000000..300ff1fb
--- /dev/null
+++ b/parse-time-string/README
@@ -0,0 +1,9 @@
+PARSE TIME STRING
+=================
+
+parse_time_string() is a date/time parser originally written for
+notmuch by Jani Nikula <jani@nikula.org>. However, there is nothing
+notmuch specific in it, and it should be kept reusable for other
+projects, and ready to be packaged on its own as needed. Please do not
+add dependencies on or references to anything notmuch specific. The
+parser should only depend on the C library.
diff --git a/parse-time-string/parse-time-string.c b/parse-time-string/parse-time-string.c
new file mode 100644
index 00000000..584067d3
--- /dev/null
+++ b/parse-time-string/parse-time-string.c
@@ -0,0 +1,1503 @@
+/*
+ * parse time string - user friendly date and time parser
+ * Copyright © 2012 Jani Nikula
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Author: Jani Nikula <jani@nikula.org>
+ */
+
+#include <assert.h>
+#include <ctype.h>
+#include <errno.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+#include <time.h>
+#include <sys/time.h>
+#include <sys/types.h>
+
+#include "parse-time-string.h"
+
+/*
+ * IMPLEMENTATION DETAILS
+ *
+ * At a high level, the parsing is done in two phases: 1) actual
+ * parsing of the input string and storing the parsed data into
+ * 'struct state', and 2) processing of the data in 'struct state'
+ * according to current time (or provided reference time) and
+ * rounding. This is evident in the main entry point function
+ * parse_time_string().
+ *
+ * 1) The parsing phase - parse_input()
+ *
+ * Parsing is greedy and happens from left to right. The parsing is as
+ * unambiguous as possible; only unambiguous date/time formats are
+ * accepted. Redundant or contradictory absolute date/time in the
+ * input (e.g. date specified multiple times/ways) is not
+ * accepted. Relative date/time on the other hand just accumulates if
+ * present multiple times (e.g. "5 days 5 days" just turns into 10
+ * days).
+ *
+ * Parsing decisions are made on the input format, not value. For
+ * example, "20/5/2005" fails because the recognized format here is
+ * MM/D/YYYY, even though the values would suggest DD/M/YYYY.
+ *
+ * Parsing is mostly stateless in the sense that parsing decisions are
+ * not made based on the values of previously parsed data, or whether
+ * certain data is present in the first place. (There are a few
+ * exceptions to the latter part, though, such as parsing of time zone
+ * that would otherwise look like plain time.)
+ *
+ * When the parser encounters a number that is not greedily parsed as
+ * part of a format, the interpretation is postponed until the next
+ * token is parsed. The parser for the next token may consume the
+ * previously postponed number. For example, when parsing "20 May" the
+ * meaning of "20" is not known until "May" is parsed. If the parser
+ * for the next token does not consume the postponed number, the
+ * number is handled as a "lone" number before parser for the next
+ * token finishes.
+ *
+ * 2) The processing phase - create_output()
+ *
+ * Once the parser in phase 1 has finished, 'struct state' contains
+ * all the information from the input string, and it's no longer
+ * needed. Since the parser does not even handle the concept of "now",
+ * the processing initializes the fields referring to the current
+ * date/time.
+ *
+ * If requested, the result is rounded towards past or future. The
+ * idea behind rounding is to support parsing date/time ranges in an
+ * obvious way. For example, for a range defined as two dates (without
+ * time), one would typically want to have an inclusive range from the
+ * beginning of start date to the end of the end date. The caller
+ * would use rounding towards past in the start date, and towards
+ * future in the end date.
+ *
+ * The absolute date and time is shifted by the relative date and
+ * time, and time zone adjustments are made. Daylight saving time
+ * (DST) is specifically *not* handled at all.
+ *
+ * Finally, the result is stored to time_t.
+ */
+
+#define unused(x) x __attribute__ ((unused))
+
+/* XXX: Redefine these to add i18n support. The keyword table uses
+ * N_() to mark strings to be translated; they are accessed
+ * dynamically using _(). */
+#define _(s) (s)	/* i18n: define as gettext (s) */
+#define N_(s) (s)	/* i18n: define as gettext_noop (s) */
+
+#define ARRAY_SIZE(a) (sizeof (a) / sizeof (a[0]))
+
+/*
+ * Field indices in the tm and set arrays of struct state.
+ *
+ * NOTE: There's some code that depends on the ordering of this enum.
+ */
+enum field {
+    /* Keep SEC...YEAR in this order. */
+    TM_ABS_SEC,		/* seconds */
+    TM_ABS_MIN,		/* minutes */
+    TM_ABS_HOUR,	/* hours */
+    TM_ABS_MDAY,	/* day of the month */
+    TM_ABS_MON,		/* month */
+    TM_ABS_YEAR,	/* year */
+
+    TM_WDAY,		/* day of the week. special: may be relative */
+    TM_ABS_ISDST,	/* daylight saving time */
+
+    TM_AMPM,		/* am vs. pm */
+    TM_TZ,		/* timezone in minutes */
+
+    /* Keep SEC...YEAR in this order. */
+    TM_REL_SEC,		/* seconds relative to absolute or reference time */
+    TM_REL_MIN,		/* minutes ... */
+    TM_REL_HOUR,	/* hours ... */
+    TM_REL_DAY,		/* days ... */
+    TM_REL_MON,		/* months ... */
+    TM_REL_YEAR,	/* years ... */
+    TM_REL_WEEK,	/* weeks ... */
+
+    TM_NONE,		/* not a field */
+
+    TM_SIZE = TM_NONE,
+    TM_FIRST_ABS = TM_ABS_SEC,
+    TM_FIRST_REL = TM_REL_SEC,
+};
+
+/* Values for the set array of struct state. */
+enum field_set {
+    FIELD_UNSET,	/* The field has not been touched by parser. */
+    FIELD_SET,		/* The field has been set by parser. */
+    FIELD_NOW,		/* The field will be set to reference time. */
+};
+
+static enum field
+next_abs_field (enum field field)
+{
+    /* NOTE: Depends on the enum ordering. */
+    return field < TM_ABS_YEAR ? field + 1 : TM_NONE;
+}
+
+static enum field
+abs_to_rel_field (enum field field)
+{
+    assert (field <= TM_ABS_YEAR);
+
+    /* NOTE: Depends on the enum ordering. */
+    return field + (TM_FIRST_REL - TM_FIRST_ABS);
+}
+
+/* Get the smallest acceptable value for field. */
+static int
+get_field_epoch_value (enum field field)
+{
+    if (field == TM_ABS_MDAY || field == TM_ABS_MON)
+	return 1;
+    else if (field == TM_ABS_YEAR)
+	return 1970;
+    else
+	return 0;
+}
+
+/* The parsing state. */
+struct state {
+    int tm[TM_SIZE];			/* parsed date and time */
+    enum field_set set[TM_SIZE];	/* set status of tm */
+
+    enum field last_field;	/* Previously set field. */
+    char delim;
+
+    int postponed_length;	/* Number of digits in postponed value. */
+    int postponed_value;
+    char postponed_delim;	/* The delimiter preceding postponed number. */
+};
+
+/*
+ * Helpers for postponed numbers.
+ *
+ * postponed_length is the number of digits in postponed value. 0
+ * means there is no postponed number. -1 means there is a postponed
+ * number, but it comes from a keyword, and it doesn't have digits.
+ */
+static int
+get_postponed_length (struct state *state)
+{
+    return state->postponed_length;
+}
+
+/*
+ * Consume a previously postponed number. Return true if a number was
+ * in fact postponed, false otherwise. Store the postponed number's
+ * value in *v, length in the input string in *n (or -1 if the number
+ * was written out and parsed as a keyword), and the preceding
+ * delimiter to *d. If a number was not postponed, *v, *n and *d are
+ * unchanged.
+ */
+static bool
+consume_postponed_number (struct state *state, int *v, int *n, char *d)
+{
+    if (!state->postponed_length)
+	return false;
+
+    if (n)
+	*n = state->postponed_length;
+
+    if (v)
+	*v = state->postponed_value;
+
+    if (d)
+	*d = state->postponed_delim;
+
+    state->postponed_length = 0;
+    state->postponed_value = 0;
+    state->postponed_delim = 0;
+
+    return true;
+}
+
+static int parse_postponed_number (struct state *state, enum field next_field);
+
+/*
+ * Postpone a number to be handled later. If one exists already,
+ * handle it first. n may be -1 to indicate a keyword that has no
+ * number length.
+ */
+static int
+set_postponed_number (struct state *state, int v, int n)
+{
+    int r;
+    char d = state->delim;
+
+    /* Parse a previously postponed number, if any. */
+    r = parse_postponed_number (state, TM_NONE);
+    if (r)
+	return r;
+
+    state->postponed_length = n;
+    state->postponed_value = v;
+    state->postponed_delim = d;
+
+    return 0;
+}
+
+static void
+set_delim (struct state *state, char delim)
+{
+    state->delim = delim;
+}
+
+static void
+unset_delim (struct state *state)
+{
+    state->delim = 0;
+}
+
+/*
+ * Field set/get/mod helpers.
+ */
+
+/* Return true if field has been set. */
+static bool
+is_field_set (struct state *state, enum field field)
+{
+    assert (field < ARRAY_SIZE (state->tm));
+
+    return state->set[field] != FIELD_UNSET;
+}
+
+static void
+unset_field (struct state *state, enum field field)
+{
+    assert (field < ARRAY_SIZE (state->tm));
+
+    state->set[field] = FIELD_UNSET;
+    state->tm[field] = 0;
+}
+
+/*
+ * Set field to value. A field can only be set once to ensure the
+ * input does not contain redundant and potentially conflicting data.
+ */
+static int
+set_field (struct state *state, enum field field, int value)
+{
+    int r;
+
+    /* Fields can only be set once. */
+    if (is_field_set (state, field))
+	return -PARSE_TIME_ERR_ALREADYSET;
+
+    state->set[field] = FIELD_SET;
+
+    /* Parse a previously postponed number, if any. */
+    r = parse_postponed_number (state, field);
+    if (r)
+	return r;
+
+    unset_delim (state);
+
+    state->tm[field] = value;
+    state->last_field = field;
+
+    return 0;
+}
+
+/*
+ * Mark n fields in fields to be set to the reference date/time in the
+ * specified time zone, or local timezone if not specified. The fields
+ * will be initialized after parsing is complete and timezone is
+ * known.
+ */
+static int
+set_fields_to_now (struct state *state, enum field *fields, size_t n)
+{
+    size_t i;
+    int r;
+
+    for (i = 0; i < n; i++) {
+	r = set_field (state, fields[i], 0);
+	if (r)
+	    return r;
+	state->set[fields[i]] = FIELD_NOW;
+    }
+
+    return 0;
+}
+
+/* Modify field by adding value to it. To be used on relative fields,
+ * which can be modified multiple times (to accumulate). */
+static int
+add_to_field (struct state *state, enum field field, int value)
+{
+    int r;
+
+    assert (field < ARRAY_SIZE (state->tm));
+
+    state->set[field] = FIELD_SET;
+
+    /* Parse a previously postponed number, if any. */
+    r = parse_postponed_number (state, field);
+    if (r)
+	return r;
+
+    unset_delim (state);
+
+    state->tm[field] += value;
+    state->last_field = field;
+
+    return 0;
+}
+
+/*
+ * Get field value. Make sure the field is set before query. It's most
+ * likely an error to call this while parsing (for example fields set
+ * as FIELD_NOW will only be set to some value after parsing).
+ */
+static int
+get_field (struct state *state, enum field field)
+{
+    assert (field < ARRAY_SIZE (state->tm));
+
+    return state->tm[field];
+}
+
+/*
+ * Validity checkers.
+ */
+static bool is_valid_12hour (int h)
+{
+    return h >= 1 && h <= 12;
+}
+
+static bool is_valid_time (int h, int m, int s)
+{
+    /* Allow 24:00:00 to denote end of day. */
+    if (h == 24 && m == 0 && s == 0)
+	return true;
+
+    return h >= 0 && h <= 23 && m >= 0 && m <= 59 && s >= 0 && s <= 59;
+}
+
+static bool is_valid_mday (int mday)
+{
+    return mday >= 1 && mday <= 31;
+}
+
+static bool is_valid_mon (int mon)
+{
+    return mon >= 1 && mon <= 12;
+}
+
+static bool is_valid_year (int year)
+{
+    return year >= 1970;
+}
+
+static bool is_valid_date (int year, int mon, int mday)
+{
+    return is_valid_year (year) && is_valid_mon (mon) && is_valid_mday (mday);
+}
+
+/* Unset indicator for time and date set helpers. */
+#define UNSET -1
+
+/* Time set helper. No input checking. Use UNSET (-1) to leave unset. */
+static int
+set_abs_time (struct state *state, int hour, int min, int sec)
+{
+    int r;
+
+    if (hour != UNSET) {
+	if ((r = set_field (state, TM_ABS_HOUR, hour)))
+	    return r;
+    }
+
+    if (min != UNSET) {
+	if ((r = set_field (state, TM_ABS_MIN, min)))
+	    return r;
+    }
+
+    if (sec != UNSET) {
+	if ((r = set_field (state, TM_ABS_SEC, sec)))
+	    return r;
+    }
+
+    return 0;
+}
+
+/* Date set helper. No input checking. Use UNSET (-1) to leave unset. */
+static int
+set_abs_date (struct state *state, int year, int mon, int mday)
+{
+    int r;
+
+    if (year != UNSET) {
+	if ((r = set_field (state, TM_ABS_YEAR, year)))
+	    return r;
+    }
+
+    if (mon != UNSET) {
+	if ((r = set_field (state, TM_ABS_MON, mon)))
+	    return r;
+    }
+
+    if (mday != UNSET) {
+	if ((r = set_field (state, TM_ABS_MDAY, mday)))
+	    return r;
+    }
+
+    return 0;
+}
+
+/*
+ * Keyword parsing and handling.
+ */
+struct keyword;
+typedef int (*setter_t)(struct state *state, struct keyword *kw);
+
+struct keyword {
+    const char *name;	/* keyword */
+    enum field field;	/* field to set, or FIELD_NONE if N/A */
+    int value;		/* value to set, or 0 if N/A */
+    setter_t set;	/* function to use for setting, if non-NULL */
+};
+
+/*
+ * Setter callback functions for keywords.
+ */
+static int
+kw_set_rel (struct state *state, struct keyword *kw)
+{
+    int multiplier = 1;
+
+    /* Get a previously set multiplier, if any. */
+    consume_postponed_number (state, &multiplier, NULL, NULL);
+
+    /* Accumulate relative field values. */
+    return add_to_field (state, kw->field, multiplier * kw->value);
+}
+
+static int
+kw_set_number (struct state *state, struct keyword *kw)
+{
+    /* -1 = no length, from keyword. */
+    return set_postponed_number (state, kw->value, -1);
+}
+
+static int
+kw_set_month (struct state *state, struct keyword *kw)
+{
+    int n = get_postponed_length (state);
+
+    /* Consume postponed number if it could be mday. This handles "20
+     * January". */
+    if (n == 1 || n == 2) {
+	int r, v;
+
+	consume_postponed_number (state, &v, NULL, NULL);
+
+	if (!is_valid_mday (v))
+	    return -PARSE_TIME_ERR_INVALIDDATE;
+
+	r = set_field (state, TM_ABS_MDAY, v);
+	if (r)
+	    return r;
+    }
+
+    return set_field (state, kw->field, kw->value);
+}
+
+static int
+kw_set_ampm (struct state *state, struct keyword *kw)
+{
+    int n = get_postponed_length (state);
+
+    /* Consume postponed number if it could be hour. This handles
+     * "5pm". */
+    if (n == 1 || n == 2) {
+	int r, v;
+
+	consume_postponed_number (state, &v, NULL, NULL);
+
+	if (!is_valid_12hour (v))
+	    return -PARSE_TIME_ERR_INVALIDTIME;
+
+	r = set_abs_time (state, v, 0, 0);
+	if (r)
+	    return r;
+    }
+
+    return set_field (state, kw->field, kw->value);
+}
+
+static int
+kw_set_timeofday (struct state *state, struct keyword *kw)
+{
+    return set_abs_time (state, kw->value, 0, 0);
+}
+
+static int
+kw_set_today (struct state *state, unused (struct keyword *kw))
+{
+    enum field fields[] = { TM_ABS_YEAR, TM_ABS_MON, TM_ABS_MDAY };
+
+    return set_fields_to_now (state, fields, ARRAY_SIZE (fields));
+}
+
+static int
+kw_set_now (struct state *state, unused (struct keyword *kw))
+{
+    enum field fields[] = { TM_ABS_HOUR, TM_ABS_MIN, TM_ABS_SEC };
+
+    return set_fields_to_now (state, fields, ARRAY_SIZE (fields));
+}
+
+static int
+kw_set_ordinal (struct state *state, struct keyword *kw)
+{
+    int n, v;
+
+    /* Require a postponed number. */
+    if (!consume_postponed_number (state, &v, &n, NULL))
+	return -PARSE_TIME_ERR_DATEFORMAT;
+
+    /* Ordinals are mday. */
+    if (n != 1 && n != 2)
+	return -PARSE_TIME_ERR_DATEFORMAT;
+
+    /* Be strict about st, nd, rd, and lax about th. */
+    if (strcasecmp (kw->name, "st") == 0 && v != 1 && v != 21 && v != 31)
+	return -PARSE_TIME_ERR_INVALIDDATE;
+    else if (strcasecmp (kw->name, "nd") == 0 && v != 2 && v != 22)
+	return -PARSE_TIME_ERR_INVALIDDATE;
+    else if (strcasecmp (kw->name, "rd") == 0 && v != 3 && v != 23)
+	return -PARSE_TIME_ERR_INVALIDDATE;
+    else if (strcasecmp (kw->name, "th") == 0 && !is_valid_mday (v))
+	return -PARSE_TIME_ERR_INVALIDDATE;
+
+    return set_field (state, TM_ABS_MDAY, v);
+}
+
+static int
+kw_ignore (unused (struct state *state), unused (struct keyword *kw))
+{
+    return 0;
+}
+
+/*
+ * Accepted keywords.
+ *
+ * A keyword may optionally contain a '|' to indicate the minimum
+ * match length. Without one, full match is required. It's advisable
+ * to keep the minimum match parts unique across all keywords. If
+ * they're not, the first match wins.
+ *
+ * If keyword begins with '*', then the matching will be case
+ * sensitive. Otherwise the matching is case insensitive.
+ *
+ * If .set is NULL, the field specified by .field will be set to
+ * .value.
+ *
+ * Note: Observe how "m" and "mi" match minutes, "M" and "mo" and
+ * "mont" match months, but "mon" matches Monday.
+ */
+static struct keyword keywords[] = {
+    /* Weekdays. */
+    { N_("sun|day"),	TM_WDAY,	0,	NULL },
+    { N_("mon|day"),	TM_WDAY,	1,	NULL },
+    { N_("tue|sday"),	TM_WDAY,	2,	NULL },
+    { N_("wed|nesday"),	TM_WDAY,	3,	NULL },
+    { N_("thu|rsday"),	TM_WDAY,	4,	NULL },
+    { N_("fri|day"),	TM_WDAY,	5,	NULL },
+    { N_("sat|urday"),	TM_WDAY,	6,	NULL },
+
+    /* Months. */
+    { N_("jan|uary"),	TM_ABS_MON,	1,	kw_set_month },
+    { N_("feb|ruary"),	TM_ABS_MON,	2,	kw_set_month },
+    { N_("mar|ch"),	TM_ABS_MON,	3,	kw_set_month },
+    { N_("apr|il"),	TM_ABS_MON,	4,	kw_set_month },
+    { N_("may"),	TM_ABS_MON,	5,	kw_set_month },
+    { N_("jun|e"),	TM_ABS_MON,	6,	kw_set_month },
+    { N_("jul|y"),	TM_ABS_MON,	7,	kw_set_month },
+    { N_("aug|ust"),	TM_ABS_MON,	8,	kw_set_month },
+    { N_("sep|tember"),	TM_ABS_MON,	9,	kw_set_month },
+    { N_("oct|ober"),	TM_ABS_MON,	10,	kw_set_month },
+    { N_("nov|ember"),	TM_ABS_MON,	11,	kw_set_month },
+    { N_("dec|ember"),	TM_ABS_MON,	12,	kw_set_month },
+
+    /* Durations. */
+    { N_("y|ears"),	TM_REL_YEAR,	1,	kw_set_rel },
+    { N_("mo|nths"),	TM_REL_MON,	1,	kw_set_rel },
+    { N_("*M"),		TM_REL_MON,	1,	kw_set_rel },
+    { N_("w|eeks"),	TM_REL_WEEK,	1,	kw_set_rel },
+    { N_("d|ays"),	TM_REL_DAY,	1,	kw_set_rel },
+    { N_("h|ours"),	TM_REL_HOUR,	1,	kw_set_rel },
+    { N_("hr|s"),	TM_REL_HOUR,	1,	kw_set_rel },
+    { N_("mi|nutes"),	TM_REL_MIN,	1,	kw_set_rel },
+    { N_("mins"),	TM_REL_MIN,	1,	kw_set_rel },
+    { N_("*m"),		TM_REL_MIN,	1,	kw_set_rel },
+    { N_("s|econds"),	TM_REL_SEC,	1,	kw_set_rel },
+    { N_("secs"),	TM_REL_SEC,	1,	kw_set_rel },
+
+    /* Numbers. */
+    { N_("one"),	TM_NONE,	1,	kw_set_number },
+    { N_("two"),	TM_NONE,	2,	kw_set_number },
+    { N_("three"),	TM_NONE,	3,	kw_set_number },
+    { N_("four"),	TM_NONE,	4,	kw_set_number },
+    { N_("five"),	TM_NONE,	5,	kw_set_number },
+    { N_("six"),	TM_NONE,	6,	kw_set_number },
+    { N_("seven"),	TM_NONE,	7,	kw_set_number },
+    { N_("eight"),	TM_NONE,	8,	kw_set_number },
+    { N_("nine"),	TM_NONE,	9,	kw_set_number },
+    { N_("ten"),	TM_NONE,	10,	kw_set_number },
+    { N_("dozen"),	TM_NONE,	12,	kw_set_number },
+    { N_("hundred"),	TM_NONE,	100,	kw_set_number },
+
+    /* Special number forms. */
+    { N_("this"),	TM_NONE,	0,	kw_set_number },
+    { N_("last"),	TM_NONE,	1,	kw_set_number },
+
+    /* Other special keywords. */
+    { N_("yesterday"),	TM_REL_DAY,	1,	kw_set_rel },
+    { N_("today"),	TM_NONE,	0,	kw_set_today },
+    { N_("now"),	TM_NONE,	0,	kw_set_now },
+    { N_("noon"),	TM_NONE,	12,	kw_set_timeofday },
+    { N_("midnight"),	TM_NONE,	0,	kw_set_timeofday },
+    { N_("am"),		TM_AMPM,	0,	kw_set_ampm },
+    { N_("a.m."),	TM_AMPM,	0,	kw_set_ampm },
+    { N_("pm"),		TM_AMPM,	1,	kw_set_ampm },
+    { N_("p.m."),	TM_AMPM,	1,	kw_set_ampm },
+    { N_("st"),		TM_NONE,	0,	kw_set_ordinal },
+    { N_("nd"),		TM_NONE,	0,	kw_set_ordinal },
+    { N_("rd"),		TM_NONE,	0,	kw_set_ordinal },
+    { N_("th"),		TM_NONE,	0,	kw_set_ordinal },
+    { N_("ago"),       	TM_NONE,	0,	kw_ignore },
+
+    /* Timezone codes: offset in minutes. XXX: Add more codes. */
+    { N_("pst"),	TM_TZ,		-8*60,	NULL },
+    { N_("mst"),	TM_TZ,		-7*60,	NULL },
+    { N_("cst"),	TM_TZ,		-6*60,	NULL },
+    { N_("est"),	TM_TZ,		-5*60,	NULL },
+    { N_("ast"),	TM_TZ,		-4*60,	NULL },
+    { N_("nst"),	TM_TZ,		-(3*60+30),	NULL },
+
+    { N_("gmt"),	TM_TZ,		0,	NULL },
+    { N_("utc"),	TM_TZ,		0,	NULL },
+
+    { N_("wet"),	TM_TZ,		0,	NULL },
+    { N_("cet"),	TM_TZ,		1*60,	NULL },
+    { N_("eet"),	TM_TZ,		2*60,	NULL },
+    { N_("fet"),	TM_TZ,		3*60,	NULL },
+
+    { N_("wat"),	TM_TZ,		1*60,	NULL },
+    { N_("cat"),	TM_TZ,		2*60,	NULL },
+    { N_("eat"),	TM_TZ,		3*60,	NULL },
+};
+
+/*
+ * Compare strings str and keyword. Return the number of matching
+ * chars on match, 0 for no match.
+ *
+ * All of the alphabetic characters (isalpha) in str up to the first
+ * non-alpha character (or end of string) must match the
+ * keyword. Consequently, the value returned on match is the number of
+ * consecutive alphabetic characters in str.
+ *
+ * Abbreviated match is accepted if the keyword contains a '|'
+ * character, and str matches keyword up to that character. Any alpha
+ * characters after that in str must still match the keyword following
+ * the '|' character. If no '|' is present, all of keyword must match.
+ *
+ * Excessive, consecutive, and misplaced (at the beginning or end) '|'
+ * characters in keyword are handled gracefully. Only the first one
+ * matters.
+ *
+ * If match_case is true, the matching is case sensitive.
+ */
+static size_t
+match_keyword (const char *str, const char *keyword, bool match_case)
+{
+    const char *s = str;
+    bool prefix_matched = false;
+
+    for (;;) {
+	while (*keyword == '|') {
+	    prefix_matched = true;
+	    keyword++;
+	}
+
+	if (!*s || !isalpha ((unsigned char) *s) || !*keyword)
+	    break;
+
+	if (match_case) {
+	    if (*s != *keyword)
+		return 0;
+	} else {
+	    if (tolower ((unsigned char) *s) !=
+		tolower ((unsigned char) *keyword))
+		return 0;
+	}
+	s++;
+	keyword++;
+    }
+
+    /* did not match all of the keyword in input string */
+    if (*s && isalpha ((unsigned char) *s))
+	return 0;
+
+    /* did not match enough of keyword */
+    if (*keyword && !prefix_matched)
+	return 0;
+
+    return s - str;
+}
+
+/*
+ * Parse a keyword. Return < 0 on error, number of parsed chars on
+ * success.
+ */
+static ssize_t
+parse_keyword (struct state *state, const char *s)
+{
+    unsigned int i;
+    size_t n = 0;
+    struct keyword *kw = NULL;
+    int r;
+
+    for (i = 0; i < ARRAY_SIZE (keywords); i++) {
+	const char *keyword = _(keywords[i].name);
+	bool mcase = false;
+
+	/* Match case if keyword begins with '*'. */
+	if (*keyword == '*') {
+	    mcase = true;
+	    keyword++;
+	}
+
+	n = match_keyword (s, keyword, mcase);
+	if (n) {
+	    kw = &keywords[i];
+	    break;
+	}
+    }
+
+    if (!kw)
+	return -PARSE_TIME_ERR_KEYWORD;
+
+    if (kw->set)
+	r = kw->set (state, kw);
+    else
+	r = set_field (state, kw->field, kw->value);
+
+    if (r < 0)
+	return r;
+
+    return n;
+}
+
+/*
+ * Non-keyword parsers and their helpers.
+ */
+
+static int
+set_user_tz (struct state *state, char sign, int hour, int min)
+{
+    int tz = hour * 60 + min;
+
+    assert (sign == '+' || sign == '-');
+
+    if (hour < 0 || hour > 14 || min < 0 || min > 59 || min % 15)
+	return -PARSE_TIME_ERR_INVALIDTIME;
+
+    if (sign == '-')
+	tz = -tz;
+
+    return set_field (state, TM_TZ, tz);
+}
+
+/*
+ * Parse a previously postponed number if one exists. Independent
+ * parsing of a postponed number when it wasn't consumed during
+ * parsing of the following token.
+ */
+static int
+parse_postponed_number (struct state *state, unused (enum field next_field))
+{
+    int v, n;
+    char d;
+
+    /* Bail out if there's no postponed number. */
+    if (!consume_postponed_number (state, &v, &n, &d))
+	return 0;
+
+    if (n == 1 || n == 2) {
+	/* Notable exception: Previous field affects parsing. This
+	 * handles "January 20". */
+	if (state->last_field == TM_ABS_MON) {
+	    /* D[D] */
+	    if (!is_valid_mday (v))
+		return -PARSE_TIME_ERR_INVALIDDATE;
+
+	    return set_field (state, TM_ABS_MDAY, v);
+	} else if (n == 2) {
+	    /* XXX: Only allow if last field is hour, min, or sec? */
+	    if (d == '+' || d == '-') {
+		/* +/-HH */
+		return set_user_tz (state, d, v, 0);
+	    }
+	}
+    } else if (n == 4) {
+	/* Notable exception: Value affects parsing. Time zones are
+	 * always at most 1400 and we don't understand years before
+	 * 1970. */
+	if (!is_valid_year (v)) {
+	    if (d == '+' || d == '-') {
+		/* +/-HHMM */
+		return set_user_tz (state, d, v / 100, v % 100);
+	    }
+	} else {
+	    /* YYYY */
+	    return set_field (state, TM_ABS_YEAR, v);
+	}
+    } else if (n == 6) {
+	/* HHMMSS */
+	int hour = v / 10000;
+	int min = (v / 100) % 100;
+	int sec = v % 100;
+
+	if (!is_valid_time (hour, min, sec))
+	    return -PARSE_TIME_ERR_INVALIDTIME;
+
+	return set_abs_time (state, hour, min, sec);
+    } else if (n == 8) {
+	/* YYYYMMDD */
+	int year = v / 10000;
+	int mon = (v / 100) % 100;
+	int mday = v % 100;
+
+	if (!is_valid_date (year, mon, mday))
+	    return -PARSE_TIME_ERR_INVALIDDATE;
+
+	return set_abs_date (state, year, mon, mday);
+    }
+
+    return -PARSE_TIME_ERR_FORMAT;
+}
+
+static int tm_get_field (const struct tm *tm, enum field field);
+
+static int
+set_timestamp (struct state *state, time_t t)
+{
+    struct tm tm;
+    enum field f;
+    int r;
+
+    if (gmtime_r (&t, &tm) == NULL)
+	return -PARSE_TIME_ERR_LIB;
+
+    for (f = TM_ABS_SEC; f != TM_NONE; f = next_abs_field (f)) {
+	r = set_field (state, f, tm_get_field (&tm, f));
+	if (r)
+	    return r;
+    }
+
+    r = set_field (state, TM_TZ, 0);
+    if (r)
+	return r;
+
+    /* XXX: Prevent TM_AMPM with timestamp, e.g. "@123456 pm" */
+
+    return 0;
+}
+
+/* Parse a single number. Typically postpone parsing until later. */
+static int
+parse_single_number (struct state *state, unsigned long v,
+		     unsigned long n)
+{
+    assert (n);
+
+    if (state->delim == '@')
+	return set_timestamp (state, (time_t) v);
+
+    if (v > INT_MAX)
+	return -PARSE_TIME_ERR_FORMAT;
+
+    return set_postponed_number (state, v, n);
+}
+
+static bool
+is_time_sep (char c)
+{
+    return c == ':';
+}
+
+static bool
+is_date_sep (char c)
+{
+    return c == '/' || c == '-' || c == '.';
+}
+
+static bool
+is_sep (char c)
+{
+    return is_time_sep (c) || is_date_sep (c);
+}
+
+/* Two-digit year: 00...69 is 2000s, 70...99 1900s, if n == 0 keep
+ * unset. */
+static int
+expand_year (unsigned long year, size_t n)
+{
+    if (n == 2) {
+	return (year < 70 ? 2000 : 1900) + year;
+    } else if (n == 4) {
+	return year;
+    } else {
+	return UNSET;
+    }
+}
+
+/* Parse a date number triplet. */
+static int
+parse_date (struct state *state, char sep,
+	    unsigned long v1, unsigned long v2, unsigned long v3,
+	    size_t n1, size_t n2, size_t n3)
+{
+    int year = UNSET, mon = UNSET, mday = UNSET;
+
+    assert (is_date_sep (sep));
+
+    switch (sep) {
+    case '/': /* Date: M[M]/D[D][/YY[YY]] or M[M]/YYYY */
+	if (n1 != 1 && n1 != 2)
+	    return -PARSE_TIME_ERR_DATEFORMAT;
+
+	if ((n2 == 1 || n2 == 2) && (n3 == 0 || n3 == 2 || n3 == 4)) {
+	    /* M[M]/D[D][/YY[YY]] */
+	    year = expand_year (v3, n3);
+	    mon = v1;
+	    mday = v2;
+	} else if (n2 == 4 && n3 == 0) {
+	    /* M[M]/YYYY */
+	    year = v2;
+	    mon = v1;
+	} else {
+	    return -PARSE_TIME_ERR_DATEFORMAT;
+	}
+	break;
+
+    case '-': /* Date: YYYY-MM[-DD] or DD-MM[-YY[YY]] or MM-YYYY */
+	if (n1 == 4 && n2 == 2 && (n3 == 0 || n3 == 2)) {
+	    /* YYYY-MM[-DD] */
+	    year = v1;
+	    mon = v2;
+	    if (n3)
+		mday = v3;
+	} else if (n1 == 2 && n2 == 2 && (n3 == 0 || n3 == 2 || n3 == 4)) {
+	    /* DD-MM[-YY[YY]] */
+	    year = expand_year (v3, n3);
+	    mon = v2;
+	    mday = v1;
+	} else if (n1 == 2 && n2 == 4 && n3 == 0) {
+	    /* MM-YYYY */
+	    year = v2;
+	    mon = v1;
+	} else {
+	    return -PARSE_TIME_ERR_DATEFORMAT;
+	}
+	break;
+
+    case '.': /* Date: D[D].M[M][.[YY[YY]]] */
+	if ((n1 != 1 && n1 != 2) || (n2 != 1 && n2 != 2) ||
+	    (n3 != 0 && n3 != 2 && n3 != 4))
+	    return -PARSE_TIME_ERR_DATEFORMAT;
+
+	year = expand_year (v3, n3);
+	mon = v2;
+	mday = v1;
+	break;
+    }
+
+    if (year != UNSET && !is_valid_year (year))
+	return -PARSE_TIME_ERR_INVALIDDATE;
+
+    if (mon != UNSET && !is_valid_mon (mon))
+	return -PARSE_TIME_ERR_INVALIDDATE;
+
+    if (mday != UNSET && !is_valid_mday (mday))
+	return -PARSE_TIME_ERR_INVALIDDATE;
+
+    return set_abs_date (state, year, mon, mday);
+}
+
+/* Parse a time number triplet. */
+static int
+parse_time (struct state *state, char sep,
+	    unsigned long v1, unsigned long v2, unsigned long v3,
+	    size_t n1, size_t n2, size_t n3)
+{
+    assert (is_time_sep (sep));
+
+    if ((n1 != 1 && n1 != 2) || n2 != 2 || (n3 != 0 && n3 != 2))
+	return -PARSE_TIME_ERR_TIMEFORMAT;
+
+    /*
+     * Notable exception: Previously set fields affect
+     * parsing. Interpret (+|-)HH:MM as time zone only if hour and
+     * minute have been set.
+     *
+     * XXX: This could be fixed by restricting the delimiters
+     * preceding time. For '+' it would be justified, but for '-' it
+     * might be inconvenient. However prefer to allow '-' as an
+     * insignificant delimiter preceding time for convenience, and
+     * handle '+' the same way for consistency between positive and
+     * negative time zones.
+     */
+    if (is_field_set (state, TM_ABS_HOUR) &&
+	is_field_set (state, TM_ABS_MIN) &&
+	n1 == 2 && n2 == 2 && n3 == 0 &&
+	(state->delim == '+' || state->delim == '-')) {
+	return set_user_tz (state, state->delim, v1, v2);
+    }
+
+    if (!is_valid_time (v1, v2, v3))
+	return -PARSE_TIME_ERR_INVALIDTIME;
+
+    return set_abs_time (state, v1, v2, n3 ? v3 : 0);
+}
+
+/* strtoul helper that assigns length. */
+static unsigned long
+strtoul_len (const char *s, const char **endp, size_t *len)
+{
+    unsigned long val = strtoul (s, (char **) endp, 10);
+
+    *len = *endp - s;
+    return val;
+}
+
+/*
+ * Parse a (group of) number(s). Return < 0 on error, number of parsed
+ * chars on success.
+ */
+static ssize_t
+parse_number (struct state *state, const char *s)
+{
+    int r;
+    unsigned long v1, v2, v3 = 0;
+    size_t n1, n2, n3 = 0;
+    const char *p = s;
+    char sep;
+
+    v1 = strtoul_len (p, &p, &n1);
+
+    if (!is_sep (*p) || !isdigit ((unsigned char) *(p + 1))) {
+	/* A single number. */
+	r = parse_single_number (state, v1, n1);
+	if (r)
+	    return r;
+
+	return p - s;
+    }
+
+    sep = *p;
+    v2 = strtoul_len (p + 1, &p, &n2);
+
+    /* A group of two or three numbers? */
+    if (*p == sep && isdigit ((unsigned char) *(p + 1)))
+	v3 = strtoul_len (p + 1, &p, &n3);
+
+    if (is_time_sep (sep))
+	r = parse_time (state, sep, v1, v2, v3, n1, n2, n3);
+    else
+	r = parse_date (state, sep, v1, v2, v3, n1, n2, n3);
+
+    if (r)
+	return r;
+
+    return p - s;
+}
+
+/*
+ * Parse delimiter(s). Throw away all except the last one, which is
+ * stored for parsing the next non-delimiter. Return < 0 on error,
+ * number of parsed chars on success.
+ *
+ * XXX: We might want to be more strict here.
+ */
+static ssize_t
+parse_delim (struct state *state, const char *s)
+{
+    const char *p = s;
+
+    /*
+     * Skip non-alpha and non-digit, and store the last for further
+     * processing.
+     */
+    while (*p && !isalnum ((unsigned char) *p)) {
+	set_delim (state, *p);
+	p++;
+    }
+
+    return p - s;
+}
+
+/*
+ * Parse a date/time string. Return < 0 on error, number of parsed
+ * chars on success.
+ */
+static ssize_t
+parse_input (struct state *state, const char *s)
+{
+    const char *p = s;
+    ssize_t n;
+    int r;
+
+    while (*p) {
+	if (isalpha ((unsigned char) *p)) {
+	    n = parse_keyword (state, p);
+	} else if (isdigit ((unsigned char) *p)) {
+	    n = parse_number (state, p);
+	} else {
+	    n = parse_delim (state, p);
+	}
+
+	if (n <= 0) {
+	    if (n == 0)
+		n = -PARSE_TIME_ERR;
+
+	    return n;
+	}
+
+	p += n;
+    }
+
+    /* Parse a previously postponed number, if any. */
+    r = parse_postponed_number (state, TM_NONE);
+    if (r < 0)
+	return r;
+
+    return p - s;
+}
+
+/*
+ * Processing the parsed input.
+ */
+
+/*
+ * Initialize reference time to tm. Use time zone in state if
+ * specified, otherwise local time. Use now for reference time if
+ * non-NULL, otherwise current time.
+ */
+static int
+initialize_now (struct state *state, const time_t *ref, struct tm *tm)
+{
+    time_t t;
+
+    if (ref) {
+	t = *ref;
+    } else {
+	if (time (&t) == (time_t) -1)
+	    return -PARSE_TIME_ERR_LIB;
+    }
+
+    if (is_field_set (state, TM_TZ)) {
+	/* Some other time zone. */
+
+	/* Adjust now according to the TZ. */
+	t += get_field (state, TM_TZ) * 60;
+
+	/* It's not gm, but this doesn't mess with the TZ. */
+	if (gmtime_r (&t, tm) == NULL)
+	    return -PARSE_TIME_ERR_LIB;
+    } else {
+	/* Local time. */
+	if (localtime_r (&t, tm) == NULL)
+	    return -PARSE_TIME_ERR_LIB;
+    }
+
+    return 0;
+}
+
+/*
+ * Normalize tm according to mktime(3); if structure members are
+ * outside their valid interval, they will be normalized (so that, for
+ * example, 40 October is changed into 9 November), and tm_wday and
+ * tm_yday are set to values determined from the contents of the other
+ * fields.
+ *
+ * Both mktime(3) and localtime_r(3) use local time, but they cancel
+ * each other out here, making this function agnostic to time zone.
+ */
+static int
+normalize_tm (struct tm *tm)
+{
+    time_t t = mktime (tm);
+
+    if (t == (time_t) -1)
+	return -PARSE_TIME_ERR_LIB;
+
+    if (!localtime_r (&t, tm))
+	return -PARSE_TIME_ERR_LIB;
+
+    return 0;
+}
+
+/* Get field out of a struct tm. */
+static int
+tm_get_field (const struct tm *tm, enum field field)
+{
+    switch (field) {
+    case TM_ABS_SEC:	return tm->tm_sec;
+    case TM_ABS_MIN:	return tm->tm_min;
+    case TM_ABS_HOUR:	return tm->tm_hour;
+    case TM_ABS_MDAY:	return tm->tm_mday;
+    case TM_ABS_MON:	return tm->tm_mon + 1; /* 0- to 1-based */
+    case TM_ABS_YEAR:	return 1900 + tm->tm_year;
+    case TM_WDAY:	return tm->tm_wday;
+    case TM_ABS_ISDST:	return tm->tm_isdst;
+    default:
+	assert (false);
+	break;
+    }
+
+    return 0;
+}
+
+/* Modify hour according to am/pm setting. */
+static int
+fixup_ampm (struct state *state)
+{
+    int hour, hdiff = 0;
+
+    if (!is_field_set (state, TM_AMPM))
+	return 0;
+
+    if (!is_field_set (state, TM_ABS_HOUR))
+	return -PARSE_TIME_ERR_TIMEFORMAT;
+
+    hour = get_field (state, TM_ABS_HOUR);
+    if (!is_valid_12hour (hour))
+	return -PARSE_TIME_ERR_INVALIDTIME;
+
+    if (get_field (state, TM_AMPM)) {
+	/* 12pm is noon. */
+	if (hour != 12)
+	    hdiff = 12;
+    } else {
+	/* 12am is midnight, beginning of day. */
+	if (hour == 12)
+	    hdiff = -12;
+    }
+
+    add_to_field (state, TM_REL_HOUR, -hdiff);
+
+    return 0;
+}
+
+/* Combine absolute and relative fields, and round. */
+static int
+create_output (struct state *state, time_t *t_out, const time_t *ref,
+	       int round)
+{
+    struct tm tm = { .tm_isdst = -1 };
+    struct tm now;
+    time_t t;
+    enum field f;
+    int r;
+    int week_round = PARSE_TIME_NO_ROUND;
+
+    r = initialize_now (state, ref, &now);
+    if (r)
+	return r;
+
+    /* Initialize fields flagged as "now" to reference time. */
+    for (f = TM_ABS_SEC; f != TM_NONE; f = next_abs_field (f)) {
+	if (state->set[f] == FIELD_NOW) {
+	    state->tm[f] = tm_get_field (&now, f);
+	    state->set[f] = FIELD_SET;
+	}
+    }
+
+    /*
+     * If WDAY is set but MDAY is not, we consider WDAY relative
+     *
+     * XXX: This fails on stuff like "two months monday" because two
+     * months ago wasn't the same day as today. Postpone until we know
+     * date?
+     */
+    if (is_field_set (state, TM_WDAY) &&
+	!is_field_set (state, TM_ABS_MDAY)) {
+	int wday = get_field (state, TM_WDAY);
+	int today = tm_get_field (&now, TM_WDAY);
+	int rel_days;
+
+	if (today > wday)
+	    rel_days = today - wday;
+	else
+	    rel_days = today + 7 - wday;
+
+	/* This also prevents special week rounding from happening. */
+	add_to_field (state, TM_REL_DAY, rel_days);
+
+	unset_field (state, TM_WDAY);
+    }
+
+    r = fixup_ampm (state);
+    if (r)
+	return r;
+
+    /*
+     * Iterate fields from most accurate to least accurate, and set
+     * unset fields according to requested rounding.
+     */
+    for (f = TM_ABS_SEC; f != TM_NONE; f = next_abs_field (f)) {
+	if (round != PARSE_TIME_NO_ROUND) {
+	    enum field r = abs_to_rel_field (f);
+
+	    if (is_field_set (state, f) || is_field_set (state, r)) {
+		if (round >= PARSE_TIME_ROUND_UP && f != TM_ABS_SEC) {
+		    /*
+		     * This is the most accurate field
+		     * specified. Round up adjusting it towards
+		     * future.
+		     */
+		    add_to_field (state, r, -1);
+
+		    /*
+		     * Go back a second if the result is to be used
+		     * for inclusive comparisons.
+		     */
+		    if (round == PARSE_TIME_ROUND_UP_INCLUSIVE)
+			add_to_field (state, TM_REL_SEC, 1);
+		}
+		round = PARSE_TIME_NO_ROUND; /* No more rounding. */
+	    } else {
+		if (f == TM_ABS_MDAY &&
+		    is_field_set (state, TM_REL_WEEK)) {
+		    /* Week is most accurate. */
+		    week_round = round;
+		    round = PARSE_TIME_NO_ROUND;
+		} else {
+		    set_field (state, f, get_field_epoch_value (f));
+		}
+	    }
+	}
+
+	if (!is_field_set (state, f))
+	    set_field (state, f, tm_get_field (&now, f));
+    }
+
+    /* Special case: rounding with week accuracy. */
+    if (week_round != PARSE_TIME_NO_ROUND) {
+	/* Temporarily set more accurate fields to now. */
+	set_field (state, TM_ABS_SEC, tm_get_field (&now, TM_ABS_SEC));
+	set_field (state, TM_ABS_MIN, tm_get_field (&now, TM_ABS_MIN));
+	set_field (state, TM_ABS_HOUR, tm_get_field (&now, TM_ABS_HOUR));
+	set_field (state, TM_ABS_MDAY, tm_get_field (&now, TM_ABS_MDAY));
+    }
+
+    /*
+     * Set all fields. They may contain out of range values before
+     * normalization by mktime(3).
+     */
+    tm.tm_sec = get_field (state, TM_ABS_SEC) - get_field (state, TM_REL_SEC);
+    tm.tm_min = get_field (state, TM_ABS_MIN) - get_field (state, TM_REL_MIN);
+    tm.tm_hour = get_field (state, TM_ABS_HOUR) - get_field (state, TM_REL_HOUR);
+    tm.tm_mday = get_field (state, TM_ABS_MDAY) -
+		 get_field (state, TM_REL_DAY) - 7 * get_field (state, TM_REL_WEEK);
+    tm.tm_mon = get_field (state, TM_ABS_MON) - get_field (state, TM_REL_MON);
+    tm.tm_mon--; /* 1- to 0-based */
+    tm.tm_year = get_field (state, TM_ABS_YEAR) - get_field (state, TM_REL_YEAR) - 1900;
+
+    /*
+     * It's always normal time.
+     *
+     * XXX: This is probably not a solution that universally
+     * works. Just make sure DST is not taken into account. We don't
+     * want rounding to be affected by DST.
+     */
+    tm.tm_isdst = -1;
+
+    /* Special case: rounding with week accuracy. */
+    if (week_round != PARSE_TIME_NO_ROUND) {
+	/* Normalize to get proper tm.wday. */
+	r = normalize_tm (&tm);
+	if (r < 0)
+	    return r;
+
+	/* Set more accurate fields back to zero. */
+	tm.tm_sec = 0;
+	tm.tm_min = 0;
+	tm.tm_hour = 0;
+	tm.tm_isdst = -1;
+
+	/* Monday is the true 1st day of week, but this is easier. */
+	if (week_round >= PARSE_TIME_ROUND_UP) {
+	    tm.tm_mday += 7 - tm.tm_wday;
+	    if (week_round == PARSE_TIME_ROUND_UP_INCLUSIVE)
+		tm.tm_sec--;
+	} else {
+	    tm.tm_mday -= tm.tm_wday;
+	}
+    }
+
+    if (is_field_set (state, TM_TZ)) {
+	/* tm is in specified TZ, convert to UTC for timegm(3). */
+	tm.tm_min -= get_field (state, TM_TZ);
+	t = timegm (&tm);
+    } else {
+	/* tm is in local time. */
+	t = mktime (&tm);
+    }
+
+    if (t == (time_t) -1)
+	return -PARSE_TIME_ERR_LIB;
+
+    *t_out = t;
+
+    return 0;
+}
+
+/* Internally, all errors are < 0. parse_time_string() returns errors > 0. */
+#define EXTERNAL_ERR(r) (-r)
+
+int
+parse_time_string (const char *s, time_t *t, const time_t *ref, int round)
+{
+    struct state state = { .last_field = TM_NONE };
+    int r;
+
+    if (!s || !t)
+	return EXTERNAL_ERR (-PARSE_TIME_ERR);
+
+    r = parse_input (&state, s);
+    if (r < 0)
+	return EXTERNAL_ERR (r);
+
+    r = create_output (&state, t, ref, round);
+    if (r < 0)
+	return EXTERNAL_ERR (r);
+
+    return 0;
+}
diff --git a/parse-time-string/parse-time-string.h b/parse-time-string/parse-time-string.h
new file mode 100644
index 00000000..bfa4ee35
--- /dev/null
+++ b/parse-time-string/parse-time-string.h
@@ -0,0 +1,102 @@
+/*
+ * parse time string - user friendly date and time parser
+ * Copyright © 2012 Jani Nikula
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Author: Jani Nikula <jani@nikula.org>
+ */
+
+#ifndef PARSE_TIME_STRING_H
+#define PARSE_TIME_STRING_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <time.h>
+
+/* return values for parse_time_string() */
+enum {
+    PARSE_TIME_OK = 0,
+    PARSE_TIME_ERR,		/* unspecified error */
+    PARSE_TIME_ERR_LIB,		/* library call failed */
+    PARSE_TIME_ERR_ALREADYSET,	/* attempt to set unit twice */
+    PARSE_TIME_ERR_FORMAT,	/* generic date/time format error */
+    PARSE_TIME_ERR_DATEFORMAT,	/* date format error */
+    PARSE_TIME_ERR_TIMEFORMAT,	/* time format error */
+    PARSE_TIME_ERR_INVALIDDATE,	/* date value error */
+    PARSE_TIME_ERR_INVALIDTIME,	/* time value error */
+    PARSE_TIME_ERR_KEYWORD,	/* unknown keyword */
+};
+
+/* round values for parse_time_string() */
+enum {
+    PARSE_TIME_ROUND_DOWN = -1,
+    PARSE_TIME_NO_ROUND = 0,
+    PARSE_TIME_ROUND_UP = 1,
+    PARSE_TIME_ROUND_UP_INCLUSIVE = 2,
+};
+
+/**
+ * parse_time_string() - user friendly date and time parser
+ * @s:		string to parse
+ * @t:		pointer to time_t to store parsed time in
+ * @ref:	pointer to time_t containing reference date/time, or NULL
+ * @round:	PARSE_TIME_NO_ROUND, PARSE_TIME_ROUND_DOWN, or
+ *		PARSE_TIME_ROUND_UP
+ *
+ * Parse a date/time string 's' and store the parsed date/time result
+ * in 't'.
+ *
+ * A reference date/time is used for determining the "date/time units"
+ * (roughly equivalent to struct tm members) not specified by 's'. If
+ * 'ref' is non-NULL, it must contain a pointer to a time_t to be used
+ * as reference date/time. Otherwise, the current time is used.
+ *
+ * If 's' does not specify a full date/time, the 'round' parameter
+ * specifies if and how the result should be rounded as follows:
+ *
+ *   PARSE_TIME_NO_ROUND: All date/time units that are not specified
+ *   by 's' are set to the corresponding unit derived from the
+ *   reference date/time.
+ *
+ *   PARSE_TIME_ROUND_DOWN: All date/time units that are more accurate
+ *   than the most accurate unit specified by 's' are set to the
+ *   smallest valid value for that unit. Rest of the unspecified units
+ *   are set as in PARSE_TIME_NO_ROUND.
+ *
+ *   PARSE_TIME_ROUND_UP: All date/time units that are more accurate
+ *   than the most accurate unit specified by 's' are set to the
+ *   smallest valid value for that unit. The most accurate unit
+ *   specified by 's' is incremented by one (and this is rolled over
+ *   to the less accurate units as necessary), unless the most
+ *   accurate unit is seconds. Rest of the unspecified units are set
+ *   as in PARSE_TIME_NO_ROUND.
+ *
+ *   PARSE_TIME_ROUND_UP_INCLUSIVE: Same as PARSE_TIME_ROUND_UP, minus
+ *   one second, unless the most accurate unit specified by 's' is
+ *   seconds. This is useful for callers that require a value for
+ *   inclusive comparison of the result.
+ *
+ * Return 0 (PARSE_TIME_OK) for succesfully parsed date/time, or one
+ * of PARSE_TIME_ERR_* on error. 't' is not modified on error.
+ */
+int parse_time_string (const char *s, time_t *t, const time_t *ref, int round);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* PARSE_TIME_STRING_H */