Export of internal Abseil changes.

--
f4e870453d02106c2685e0461816469a4704ad25 by Abseil Team <absl-team@google.com>:

Expose TimeZone::NextTransition() and PrevTransition() now that
we have absl::CivilSecond support in time.h.  Note that these are
for informational purposes only.  General time code should not
care when offset changes occur.

PiperOrigin-RevId: 217177292

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cfadd275c7333f7c27c4d682b9d167010d874e69 by Abseil Team <absl-team@google.com>:

Import of CCTZ from GitHub.

PiperOrigin-RevId: 217153577

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6ff5b8c61a1239b9c0478a7c62bcd2844b310307 by Jon Cohen <cohenjon@google.com>:

Fix code examples in hash_testing.h.  Includes random clang-format changes.

PiperOrigin-RevId: 216898995

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de124129d27f4627dabe193a10bf106a11783fba by Shaindel Schwartz <shaindel@google.com>:

Add contribution guidelines describing how we decide whether to include an API in Abseil.

PiperOrigin-RevId: 216886943
GitOrigin-RevId: f4e870453d02106c2685e0461816469a4704ad25
Change-Id: Ib9c6706f5bf931b71c0357bf1342053a3bee8ff7

1 files changed, 22 insertions, 0 deletions

diff --git a/absl/time/time.cc b/absl/time/time.cc
index 0703856fa327..ac2c8a8356f2 100644
--- a/absl/time/time.cc
+++ b/absl/time/time.cc
@@ -176,6 +176,20 @@ inline int MapWeekday(const cctz::weekday& wd) {
   return 1;
 }
 
+bool FindTransition(const cctz::time_zone& tz,
+                    bool (cctz::time_zone::*find_transition)(
+                        const cctz::time_point<cctz::seconds>& tp,
+                        cctz::time_zone::civil_transition* trans) const,
+                    Time t, TimeZone::CivilTransition* trans) {
+  // Transitions are second-aligned, so we can discard any fractional part.
+  const auto tp = unix_epoch() + cctz::seconds(ToUnixSeconds(t));
+  cctz::time_zone::civil_transition tr;
+  if (!(tz.*find_transition)(tp, &tr)) return false;
+  trans->from = CivilSecond(tr.from);
+  trans->to = CivilSecond(tr.to);
+  return true;
+}
+
 }  // namespace
 
 //
@@ -366,6 +380,14 @@ absl::TimeZone::TimeInfo TimeZone::At(CivilSecond ct) const {
   return ti;
 }
 
+bool TimeZone::NextTransition(Time t, CivilTransition* trans) const {
+  return FindTransition(cz_, &cctz::time_zone::next_transition, t, trans);
+}
+
+bool TimeZone::PrevTransition(Time t, CivilTransition* trans) const {
+  return FindTransition(cz_, &cctz::time_zone::prev_transition, t, trans);
+}
+
 //
 // Conversions involving time zones.
 //