SkTime: return timezone information; format in ISO-8601

Motivation: PDF/A metadata will need the creation date embedded in it.

Also, GetDateTime returns local time in Win32.  This now behaves the
same as on Unix systems.

BUG=skia:3110

Review URL: https://codereview.chromium.org/1109593002

3 files changed, 44 insertions, 2 deletions

diff --git a/src/core/SkTime.cpp b/src/core/SkTime.cpp
new file mode 100644
index 0000000000..b8e42365ef
--- /dev/null
+++ b/src/core/SkTime.cpp
@@ -0,0 +1,24 @@
+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkString.h"
+#include "SkTime.h"
+
+void SkTime::DateTime::toISO8601(SkString* dst) const {
+    if (dst) {
+        int timeZoneMinutes = SkToInt(fTimeZoneMinutes);
+        char timezoneSign = timeZoneMinutes >= 0 ? '+' : '-';
+        int timeZoneHours = abs(timeZoneMinutes) / 60;
+        timeZoneMinutes = abs(timeZoneMinutes) % 60;
+        dst->printf("%04u-%02u-%02uT%02u:%02u:%02u%c%02d:%02d",
+                    static_cast<unsigned>(fYear), static_cast<unsigned>(fMonth),
+                    static_cast<unsigned>(fDay), static_cast<unsigned>(fHour),
+                    static_cast<unsigned>(fMinute),
+                    static_cast<unsigned>(fSecond), timezoneSign, timeZoneHours,
+                    timeZoneMinutes);
+    }
+}
diff --git a/src/ports/SkTime_Unix.cpp b/src/ports/SkTime_Unix.cpp
index 6e305a16f6..2d5fa279b4 100644
--- a/src/ports/SkTime_Unix.cpp
+++ b/src/ports/SkTime_Unix.cpp
@@ -16,11 +16,15 @@ void SkTime::GetDateTime(DateTime* dt)
 {
     if (dt)
     {
+        tzset();  // initialize timezone variable;
         time_t m_time;
         time(&m_time);
         struct tm* tstruct;
         tstruct = localtime(&m_time);
+        int offset = tstruct->tm_isdst == 1 ? 60 : 0;
+
         // http://pubs.opengroup.org/onlinepubs/009695399/basedefs/time.h.html
+        dt->fTimeZoneMinutes = SkToS16(offset - timezone / 60);
         dt->fYear       = tstruct->tm_year + 1900;
         dt->fMonth      = SkToU8(tstruct->tm_mon + 1);
         dt->fDayOfWeek  = SkToU8(tstruct->tm_wday);
diff --git a/src/ports/SkTime_win.cpp b/src/ports/SkTime_win.cpp
index bc0f8f0084..19f4695a86 100644
--- a/src/ports/SkTime_win.cpp
+++ b/src/ports/SkTime_win.cpp
@@ -14,8 +14,22 @@ void SkTime::GetDateTime(DateTime* dt)
     if (dt)
     {
         SYSTEMTIME      st;
-        GetSystemTime(&st);
-
+        TIME_ZONE_INFORMATION timeZoneInfo;
+        int tz_bias;
+        GetLocalTime(&st);
+        // https://gist.github.com/wrl/8924636
+        switch (GetTimeZoneInformation(&timeZoneInfo)) {
+            case TIME_ZONE_ID_STANDARD:
+                tz_bias = -timeZoneInfo.Bias - timeZoneInfo.StandardBias;
+                break;
+            case TIME_ZONE_ID_DAYLIGHT:
+                tz_bias = -timeZoneInfo.Bias - timeZoneInfo.DaylightBias;
+                break;
+            default:
+                tz_bias = -timeZoneInfo.Bias;
+                break;
+        }
+        dt->fTimeZoneMinutes = SkToS16(tz_bias);
         dt->fYear       = st.wYear;
         dt->fMonth      = SkToU8(st.wMonth);
         dt->fDayOfWeek  = SkToU8(st.wDayOfWeek);