Export of internal Abseil changes.

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86b1c997fac1f77b0eacfab788659b5a89a6096e by Abseil Team <absl-team@google.com>:

Import of CCTZ from GitHub.

PiperOrigin-RevId: 211654320

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299b70e1247df768454a76eb957a184de9706f61 by Chris Kennelly <ckennelly@google.com>:

Avoid creating a misaligned reference to int.

PiperOrigin-RevId: 211505883

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c8fad4357ad0bfb3c5ad197c505509bc087072c9 by Abseil Team <absl-team@google.com>:

Import of CCTZ from GitHub.

PiperOrigin-RevId: 211458539

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0613feffcd36466c3e53a50758d7e8f17c001dce by Greg Falcon <gfalcon@google.com>:

Refactor a string unit test into a template function for internal purposes.

PiperOrigin-RevId: 211100748
GitOrigin-RevId: 86b1c997fac1f77b0eacfab788659b5a89a6096e
Change-Id: Ic6a932b6c27c6762dcdb3b0127f1e2be782418c1

1 files changed, 2 insertions, 6 deletions

diff --git a/absl/time/internal/cctz/include/cctz/civil_time_detail.h b/absl/time/internal/cctz/include/cctz/civil_time_detail.h
index f831258..5fe0967 100644
--- a/absl/time/internal/cctz/include/cctz/civil_time_detail.h
+++ b/absl/time/internal/cctz/include/cctz/civil_time_detail.h
@@ -508,12 +508,8 @@ CONSTEXPR_F weekday get_weekday(const civil_day& cd) noexcept {
   CONSTEXPR_D int k_weekday_offsets[1 + 12] = {
       -1, 0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4,
   };
-  year_t wd = cd.year() - (cd.month() < 3);
-  if (wd >= 0) {
-    wd += wd / 4 - wd / 100 + wd / 400;
-  } else {
-    wd += (wd - 3) / 4 - (wd - 99) / 100 + (wd - 399) / 400;
-  }
+  year_t wd = 2400 + (cd.year() % 400) - (cd.month() < 3);
+  wd += wd / 4 - wd / 100 + wd / 400;
   wd += k_weekday_offsets[cd.month()] + cd.day();
   return k_weekday_by_sun_off[(wd % 7 + 7) % 7];
 }