merge(3p/abseil_cpp): Merge upstream at 'ccdbb5941' r/1011

Change-Id: I6e85fc7b5f76bba1f1eef15e600a8acb64e97ef5

13 files changed, 304 insertions, 102 deletions

diff --git a/third_party/abseil_cpp/absl/time/civil_time.cc b/third_party/abseil_cpp/absl/time/civil_time.cc
index c4202c7399ae..bdfe9ce0efb3 100644
--- a/third_party/abseil_cpp/absl/time/civil_time.cc
+++ b/third_party/abseil_cpp/absl/time/civil_time.cc
@@ -98,26 +98,26 @@ bool ParseLenient(string_view s, CivilT* c) {
 }  // namespace
 
 std::string FormatCivilTime(CivilSecond c) {
-  return FormatYearAnd("-%m-%dT%H:%M:%S", c);
+  return FormatYearAnd("-%m-%d%ET%H:%M:%S", c);
 }
 std::string FormatCivilTime(CivilMinute c) {
-  return FormatYearAnd("-%m-%dT%H:%M", c);
+  return FormatYearAnd("-%m-%d%ET%H:%M", c);
 }
 std::string FormatCivilTime(CivilHour c) {
-  return FormatYearAnd("-%m-%dT%H", c);
+  return FormatYearAnd("-%m-%d%ET%H", c);
 }
 std::string FormatCivilTime(CivilDay c) { return FormatYearAnd("-%m-%d", c); }
 std::string FormatCivilTime(CivilMonth c) { return FormatYearAnd("-%m", c); }
 std::string FormatCivilTime(CivilYear c) { return FormatYearAnd("", c); }
 
 bool ParseCivilTime(string_view s, CivilSecond* c) {
-  return ParseYearAnd("-%m-%dT%H:%M:%S", s, c);
+  return ParseYearAnd("-%m-%d%ET%H:%M:%S", s, c);
 }
 bool ParseCivilTime(string_view s, CivilMinute* c) {
-  return ParseYearAnd("-%m-%dT%H:%M", s, c);
+  return ParseYearAnd("-%m-%d%ET%H:%M", s, c);
 }
 bool ParseCivilTime(string_view s, CivilHour* c) {
-  return ParseYearAnd("-%m-%dT%H", s, c);
+  return ParseYearAnd("-%m-%d%ET%H", s, c);
 }
 bool ParseCivilTime(string_view s, CivilDay* c) {
   return ParseYearAnd("-%m-%d", s, c);
diff --git a/third_party/abseil_cpp/absl/time/format.cc b/third_party/abseil_cpp/absl/time/format.cc
index 228940ed1b99..4005fb704cf6 100644
--- a/third_party/abseil_cpp/absl/time/format.cc
+++ b/third_party/abseil_cpp/absl/time/format.cc
@@ -27,14 +27,11 @@ namespace cctz = absl::time_internal::cctz;
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 
-ABSL_DLL extern const char RFC3339_full[] =
-    "%Y-%m-%dT%H:%M:%E*S%Ez";
-ABSL_DLL extern const char RFC3339_sec[] = "%Y-%m-%dT%H:%M:%S%Ez";
-
-ABSL_DLL extern const char RFC1123_full[] =
-    "%a, %d %b %E4Y %H:%M:%S %z";
-ABSL_DLL extern const char RFC1123_no_wday[] =
-    "%d %b %E4Y %H:%M:%S %z";
+ABSL_DLL extern const char RFC3339_full[] = "%Y-%m-%d%ET%H:%M:%E*S%Ez";
+ABSL_DLL extern const char RFC3339_sec[] = "%Y-%m-%d%ET%H:%M:%S%Ez";
+
+ABSL_DLL extern const char RFC1123_full[] = "%a, %d %b %E4Y %H:%M:%S %z";
+ABSL_DLL extern const char RFC1123_no_wday[] = "%d %b %E4Y %H:%M:%S %z";
 
 namespace {
 
diff --git a/third_party/abseil_cpp/absl/time/format_benchmark.cc b/third_party/abseil_cpp/absl/time/format_benchmark.cc
index 249c51d87586..19e481dbd1a5 100644
--- a/third_party/abseil_cpp/absl/time/format_benchmark.cc
+++ b/third_party/abseil_cpp/absl/time/format_benchmark.cc
@@ -26,7 +26,7 @@ const char* const kFormats[] = {
     absl::RFC1123_no_wday,  // 1
     absl::RFC3339_full,     // 2
     absl::RFC3339_sec,      // 3
-    "%Y-%m-%dT%H:%M:%S",    // 4
+    "%Y-%m-%d%ET%H:%M:%S",  // 4
     "%Y-%m-%d",             // 5
 };
 const int kNumFormats = sizeof(kFormats) / sizeof(kFormats[0]);
diff --git a/third_party/abseil_cpp/absl/time/internal/cctz/include/cctz/civil_time_detail.h b/third_party/abseil_cpp/absl/time/internal/cctz/include/cctz/civil_time_detail.h
index 4cde96f1aaf1..d1b4222b1f43 100644
--- a/third_party/abseil_cpp/absl/time/internal/cctz/include/cctz/civil_time_detail.h
+++ b/third_party/abseil_cpp/absl/time/internal/cctz/include/cctz/civil_time_detail.h
@@ -106,54 +106,64 @@ CONSTEXPR_F int days_per_month(year_t y, month_t m) noexcept {
 
 CONSTEXPR_F fields n_day(year_t y, month_t m, diff_t d, diff_t cd, hour_t hh,
                          minute_t mm, second_t ss) noexcept {
-  y += (cd / 146097) * 400;
+  year_t ey = y % 400;
+  const year_t oey = ey;
+  ey += (cd / 146097) * 400;
   cd %= 146097;
   if (cd < 0) {
-    y -= 400;
+    ey -= 400;
     cd += 146097;
   }
-  y += (d / 146097) * 400;
+  ey += (d / 146097) * 400;
   d = d % 146097 + cd;
   if (d > 0) {
     if (d > 146097) {
-      y += 400;
+      ey += 400;
       d -= 146097;
     }
   } else {
     if (d > -365) {
       // We often hit the previous year when stepping a civil time backwards,
       // so special case it to avoid counting up by 100/4/1-year chunks.
-      y -= 1;
-      d += days_per_year(y, m);
+      ey -= 1;
+      d += days_per_year(ey, m);
     } else {
-      y -= 400;
+      ey -= 400;
       d += 146097;
     }
   }
   if (d > 365) {
-    for (int n = days_per_century(y, m); d > n; n = days_per_century(y, m)) {
+    for (;;) {
+      int n = days_per_century(ey, m);
+      if (d <= n) break;
       d -= n;
-      y += 100;
+      ey += 100;
     }
-    for (int n = days_per_4years(y, m); d > n; n = days_per_4years(y, m)) {
+    for (;;) {
+      int n = days_per_4years(ey, m);
+      if (d <= n) break;
       d -= n;
-      y += 4;
+      ey += 4;
     }
-    for (int n = days_per_year(y, m); d > n; n = days_per_year(y, m)) {
+    for (;;) {
+      int n = days_per_year(ey, m);
+      if (d <= n) break;
       d -= n;
-      ++y;
+      ++ey;
     }
   }
   if (d > 28) {
-    for (int n = days_per_month(y, m); d > n; n = days_per_month(y, m)) {
+    for (;;) {
+      int n = days_per_month(ey, m);
+      if (d <= n) break;
       d -= n;
       if (++m > 12) {
-        ++y;
+        ++ey;
         m = 1;
       }
     }
   }
-  return fields(y, m, static_cast<day_t>(d), hh, mm, ss);
+  return fields(y + (ey - oey), m, static_cast<day_t>(d), hh, mm, ss);
 }
 CONSTEXPR_F fields n_mon(year_t y, diff_t m, diff_t d, diff_t cd, hour_t hh,
                          minute_t mm, second_t ss) noexcept {
diff --git a/third_party/abseil_cpp/absl/time/internal/cctz/include/cctz/time_zone.h b/third_party/abseil_cpp/absl/time/internal/cctz/include/cctz/time_zone.h
index d4ea90ef7eb5..5562a37bc807 100644
--- a/third_party/abseil_cpp/absl/time/internal/cctz/include/cctz/time_zone.h
+++ b/third_party/abseil_cpp/absl/time/internal/cctz/include/cctz/time_zone.h
@@ -292,6 +292,7 @@ bool parse(const std::string&, const std::string&, const time_zone&,
 //   - %E#f - Fractional seconds with # digits of precision
 //   - %E*f - Fractional seconds with full precision (a literal '*')
 //   - %E4Y - Four-character years (-999 ... -001, 0000, 0001 ... 9999)
+//   - %ET  - The RFC3339 "date-time" separator "T"
 //
 // Note that %E0S behaves like %S, and %E0f produces no characters. In
 // contrast %E*f always produces at least one digit, which may be '0'.
@@ -321,7 +322,8 @@ inline std::string format(const std::string& fmt, const time_point<D>& tp,
 // returns the corresponding time_point. Uses strftime()-like formatting
 // options, with the same extensions as cctz::format(), but with the
 // exceptions that %E#S is interpreted as %E*S, and %E#f as %E*f. %Ez
-// and %E*z also accept the same inputs.
+// and %E*z also accept the same inputs, which (along with %z) includes
+// 'z' and 'Z' as synonyms for +00:00.  %ET accepts either 'T' or 't'.
 //
 // %Y consumes as many numeric characters as it can, so the matching data
 // should always be terminated with a non-numeric. %E4Y always consumes
diff --git a/third_party/abseil_cpp/absl/time/internal/cctz/src/cctz_benchmark.cc b/third_party/abseil_cpp/absl/time/internal/cctz/src/cctz_benchmark.cc
index a402760d19e0..4e39188ff3e6 100644
--- a/third_party/abseil_cpp/absl/time/internal/cctz/src/cctz_benchmark.cc
+++ b/third_party/abseil_cpp/absl/time/internal/cctz/src/cctz_benchmark.cc
@@ -97,8 +97,8 @@ void BM_PrevWeekday(benchmark::State& state) {
 }
 BENCHMARK(BM_PrevWeekday);
 
-const char RFC3339_full[] = "%Y-%m-%dT%H:%M:%E*S%Ez";
-const char RFC3339_sec[] = "%Y-%m-%dT%H:%M:%S%Ez";
+const char RFC3339_full[] = "%Y-%m-%d%ET%H:%M:%E*S%Ez";
+const char RFC3339_sec[] = "%Y-%m-%d%ET%H:%M:%S%Ez";
 
 const char RFC1123_full[] = "%a, %d %b %Y %H:%M:%S %z";
 const char RFC1123_no_wday[] = "%d %b %Y %H:%M:%S %z";
@@ -991,12 +991,12 @@ void BM_Time_FromCivilDay0_Libc(benchmark::State& state) {
 BENCHMARK(BM_Time_FromCivilDay0_Libc);
 
 const char* const kFormats[] = {
-    RFC1123_full,         // 0
-    RFC1123_no_wday,      // 1
-    RFC3339_full,         // 2
-    RFC3339_sec,          // 3
-    "%Y-%m-%dT%H:%M:%S",  // 4
-    "%Y-%m-%d",           // 5
+    RFC1123_full,           // 0
+    RFC1123_no_wday,        // 1
+    RFC3339_full,           // 2
+    RFC3339_sec,            // 3
+    "%Y-%m-%d%ET%H:%M:%S",  // 4
+    "%Y-%m-%d",             // 5
 };
 const int kNumFormats = sizeof(kFormats) / sizeof(kFormats[0]);
 
diff --git a/third_party/abseil_cpp/absl/time/internal/cctz/src/civil_time_test.cc b/third_party/abseil_cpp/absl/time/internal/cctz/src/civil_time_test.cc
index be894d7072a4..a5a71230419f 100644
--- a/third_party/abseil_cpp/absl/time/internal/cctz/src/civil_time_test.cc
+++ b/third_party/abseil_cpp/absl/time/internal/cctz/src/civil_time_test.cc
@@ -235,6 +235,16 @@ TEST(CivilTime, Difference) {
 }
 
 // NOTE: Run this with --copt=-ftrapv to detect overflow problems.
+TEST(CivilTime, ConstructionWithHugeYear) {
+  constexpr civil_hour h(-9223372036854775807, 1, 1, -1);
+  static_assert(h.year() == -9223372036854775807 - 1,
+                "ConstructionWithHugeYear");
+  static_assert(h.month() == 12, "ConstructionWithHugeYear");
+  static_assert(h.day() == 31, "ConstructionWithHugeYear");
+  static_assert(h.hour() == 23, "ConstructionWithHugeYear");
+}
+
+// NOTE: Run this with --copt=-ftrapv to detect overflow problems.
 TEST(CivilTime, DifferenceWithHugeYear) {
   {
     constexpr civil_day d1(9223372036854775807, 1, 1);
diff --git a/third_party/abseil_cpp/absl/time/internal/cctz/src/time_zone_format.cc b/third_party/abseil_cpp/absl/time/internal/cctz/src/time_zone_format.cc
index 179975e0626e..2e02233ce118 100644
--- a/third_party/abseil_cpp/absl/time/internal/cctz/src/time_zone_format.cc
+++ b/third_party/abseil_cpp/absl/time/internal/cctz/src/time_zone_format.cc
@@ -67,6 +67,48 @@ char* strptime(const char* s, const char* fmt, std::tm* tm) {
 }
 #endif
 
+// Convert a cctz::weekday to a tm_wday value (0-6, Sunday = 0).
+int ToTmWday(weekday wd) {
+  switch (wd) {
+    case weekday::sunday:
+      return 0;
+    case weekday::monday:
+      return 1;
+    case weekday::tuesday:
+      return 2;
+    case weekday::wednesday:
+      return 3;
+    case weekday::thursday:
+      return 4;
+    case weekday::friday:
+      return 5;
+    case weekday::saturday:
+      return 6;
+  }
+  return 0; /*NOTREACHED*/
+}
+
+// Convert a tm_wday value (0-6, Sunday = 0) to a cctz::weekday.
+weekday FromTmWday(int tm_wday) {
+  switch (tm_wday) {
+    case 0:
+      return weekday::sunday;
+    case 1:
+      return weekday::monday;
+    case 2:
+      return weekday::tuesday;
+    case 3:
+      return weekday::wednesday;
+    case 4:
+      return weekday::thursday;
+    case 5:
+      return weekday::friday;
+    case 6:
+      return weekday::saturday;
+  }
+  return weekday::sunday; /*NOTREACHED*/
+}
+
 std::tm ToTM(const time_zone::absolute_lookup& al) {
   std::tm tm{};
   tm.tm_sec = al.cs.second();
@@ -84,34 +126,19 @@ std::tm ToTM(const time_zone::absolute_lookup& al) {
     tm.tm_year = static_cast<int>(al.cs.year() - 1900);
   }
 
-  switch (get_weekday(al.cs)) {
-    case weekday::sunday:
-      tm.tm_wday = 0;
-      break;
-    case weekday::monday:
-      tm.tm_wday = 1;
-      break;
-    case weekday::tuesday:
-      tm.tm_wday = 2;
-      break;
-    case weekday::wednesday:
-      tm.tm_wday = 3;
-      break;
-    case weekday::thursday:
-      tm.tm_wday = 4;
-      break;
-    case weekday::friday:
-      tm.tm_wday = 5;
-      break;
-    case weekday::saturday:
-      tm.tm_wday = 6;
-      break;
-  }
+  tm.tm_wday = ToTmWday(get_weekday(al.cs));
   tm.tm_yday = get_yearday(al.cs) - 1;
   tm.tm_isdst = al.is_dst ? 1 : 0;
   return tm;
 }
 
+// Returns the week of the year [0:53] given a civil day and the day on
+// which weeks are defined to start.
+int ToWeek(const civil_day& cd, weekday week_start) {
+  const civil_day d(cd.year() % 400, cd.month(), cd.day());
+  return static_cast<int>((d - prev_weekday(civil_year(d), week_start)) / 7);
+}
+
 const char kDigits[] = "0123456789";
 
 // Formats a 64-bit integer in the given field width.  Note that it is up
@@ -290,6 +317,7 @@ const std::int_fast64_t kExp10[kDigits10_64 + 1] = {
 //   - %E#S - Seconds with # digits of fractional precision
 //   - %E*S - Seconds with full fractional precision (a literal '*')
 //   - %E4Y - Four-character years (-999 ... -001, 0000, 0001 ... 9999)
+//   - %ET  - The RFC3339 "date-time" separator "T"
 //
 // The standard specifiers from RFC3339_* (%Y, %m, %d, %H, %M, and %S) are
 // handled internally for performance reasons.  strftime(3) is slow due to
@@ -354,7 +382,7 @@ std::string format(const std::string& format, const time_point<seconds>& tp,
     if (cur == end || (cur - percent) % 2 == 0) continue;
 
     // Simple specifiers that we handle ourselves.
-    if (strchr("YmdeHMSzZs%", *cur)) {
+    if (strchr("YmdeUuWwHMSzZs%", *cur)) {
       if (cur - 1 != pending) {
         FormatTM(&result, std::string(pending, cur - 1), tm);
       }
@@ -375,6 +403,22 @@ std::string format(const std::string& format, const time_point<seconds>& tp,
           if (*cur == 'e' && *bp == '0') *bp = ' ';  // for Windows
           result.append(bp, static_cast<std::size_t>(ep - bp));
           break;
+        case 'U':
+          bp = Format02d(ep, ToWeek(civil_day(al.cs), weekday::sunday));
+          result.append(bp, static_cast<std::size_t>(ep - bp));
+          break;
+        case 'u':
+          bp = Format64(ep, 0, tm.tm_wday ? tm.tm_wday : 7);
+          result.append(bp, static_cast<std::size_t>(ep - bp));
+          break;
+        case 'W':
+          bp = Format02d(ep, ToWeek(civil_day(al.cs), weekday::monday));
+          result.append(bp, static_cast<std::size_t>(ep - bp));
+          break;
+        case 'w':
+          bp = Format64(ep, 0, tm.tm_wday);
+          result.append(bp, static_cast<std::size_t>(ep - bp));
+          break;
         case 'H':
           bp = Format02d(ep, al.cs.hour());
           result.append(bp, static_cast<std::size_t>(ep - bp));
@@ -448,7 +492,14 @@ std::string format(const std::string& format, const time_point<seconds>& tp,
     if (*cur != 'E' || ++cur == end) continue;
 
     // Format our extensions.
-    if (*cur == 'z') {
+    if (*cur == 'T') {
+      // Formats %ET.
+      if (cur - 2 != pending) {
+        FormatTM(&result, std::string(pending, cur - 2), tm);
+      }
+      result.append("T");
+      pending = ++cur;
+    } else if (*cur == 'z') {
       // Formats %Ez.
       if (cur - 2 != pending) {
         FormatTM(&result, std::string(pending, cur - 2), tm);
@@ -551,7 +602,7 @@ const char* ParseOffset(const char* dp, const char* mode, int* offset) {
       } else {
         dp = nullptr;
       }
-    } else if (first == 'Z') {  // Zulu
+    } else if (first == 'Z' || first == 'z') {  // Zulu
       *offset = 0;
     } else {
       dp = nullptr;
@@ -602,12 +653,23 @@ const char* ParseTM(const char* dp, const char* fmt, std::tm* tm) {
   return dp;
 }
 
+// Sets year, tm_mon and tm_mday given the year, week_num, and tm_wday,
+// and the day on which weeks are defined to start.
+void FromWeek(int week_num, weekday week_start, year_t* year, std::tm* tm) {
+  const civil_year y(*year % 400);
+  civil_day cd = prev_weekday(y, week_start);  // week 0
+  cd = next_weekday(cd - 1, FromTmWday(tm->tm_wday)) + (week_num * 7);
+  *year += cd.year() - y.year();
+  tm->tm_mon = cd.month() - 1;
+  tm->tm_mday = cd.day();
+}
+
 }  // namespace
 
 // Uses strptime(3) to parse the given input.  Supports the same extended
 // format specifiers as format(), although %E#S and %E*S are treated
 // identically (and similarly for %E#f and %E*f).  %Ez and %E*z also accept
-// the same inputs.
+// the same inputs. %ET accepts either 'T' or 't'.
 //
 // The standard specifiers from RFC3339_* (%Y, %m, %d, %H, %M, and %S) are
 // handled internally so that we can normally avoid strptime() altogether
@@ -651,6 +713,8 @@ bool parse(const std::string& format, const std::string& input,
   const char* fmt = format.c_str();  // NUL terminated
   bool twelve_hour = false;
   bool afternoon = false;
+  int week_num = -1;
+  weekday week_start = weekday::sunday;
 
   bool saw_percent_s = false;
   std::int_fast64_t percent_s = 0;
@@ -689,10 +753,27 @@ bool parse(const std::string& format, const std::string& input,
       case 'm':
         data = ParseInt(data, 2, 1, 12, &tm.tm_mon);
         if (data != nullptr) tm.tm_mon -= 1;
+        week_num = -1;
         continue;
       case 'd':
       case 'e':
         data = ParseInt(data, 2, 1, 31, &tm.tm_mday);
+        week_num = -1;
+        continue;
+      case 'U':
+        data = ParseInt(data, 0, 0, 53, &week_num);
+        week_start = weekday::sunday;
+        continue;
+      case 'W':
+        data = ParseInt(data, 0, 0, 53, &week_num);
+        week_start = weekday::monday;
+        continue;
+      case 'u':
+        data = ParseInt(data, 0, 1, 7, &tm.tm_wday);
+        if (data != nullptr) tm.tm_wday %= 7;
+        continue;
+      case 'w':
+        data = ParseInt(data, 0, 0, 6, &tm.tm_wday);
         continue;
       case 'H':
         data = ParseInt(data, 2, 0, 23, &tm.tm_hour);
@@ -742,6 +823,15 @@ bool parse(const std::string& format, const std::string& input,
         data = (*data == '%' ? data + 1 : nullptr);
         continue;
       case 'E':
+        if (fmt[0] == 'T') {
+          if (*data == 'T' || *data == 't') {
+            ++data;
+            ++fmt;
+          } else {
+            data = nullptr;
+          }
+          continue;
+        }
         if (fmt[0] == 'z' || (fmt[0] == '*' && fmt[1] == 'z')) {
           data = ParseOffset(data, ":", &offset);
           if (data != nullptr) saw_offset = true;
@@ -874,6 +964,9 @@ bool parse(const std::string& format, const std::string& input,
     year += 1900;
   }
 
+  // Compute year, tm.tm_mon and tm.tm_mday if we parsed a week number.
+  if (week_num != -1) FromWeek(week_num, week_start, &year, &tm);
+
   const int month = tm.tm_mon + 1;
   civil_second cs(year, month, tm.tm_mday, tm.tm_hour, tm.tm_min, tm.tm_sec);
 
diff --git a/third_party/abseil_cpp/absl/time/internal/cctz/src/time_zone_format_test.cc b/third_party/abseil_cpp/absl/time/internal/cctz/src/time_zone_format_test.cc
index 87382e156dba..e625a839fa30 100644
--- a/third_party/abseil_cpp/absl/time/internal/cctz/src/time_zone_format_test.cc
+++ b/third_party/abseil_cpp/absl/time/internal/cctz/src/time_zone_format_test.cc
@@ -48,8 +48,8 @@ namespace {
     EXPECT_STREQ(zone, al.abbr);                                  \
   } while (0)
 
-const char RFC3339_full[] = "%Y-%m-%dT%H:%M:%E*S%Ez";
-const char RFC3339_sec[] = "%Y-%m-%dT%H:%M:%S%Ez";
+const char RFC3339_full[] = "%Y-%m-%d%ET%H:%M:%E*S%Ez";
+const char RFC3339_sec[] = "%Y-%m-%d%ET%H:%M:%S%Ez";
 
 const char RFC1123_full[] = "%a, %d %b %Y %H:%M:%S %z";
 const char RFC1123_no_wday[] = "%d %b %Y %H:%M:%S %z";
@@ -679,6 +679,34 @@ TEST(Format, RFC1123Format) {  // locale specific
   EXPECT_EQ("28 Jun 1977 09:08:07 -0700", format(RFC1123_no_wday, tp, tz));
 }
 
+TEST(Format, Week) {
+  const time_zone utc = utc_time_zone();
+
+  auto tp = convert(civil_second(2017, 1, 1, 0, 0, 0), utc);
+  EXPECT_EQ("2017-01-7", format("%Y-%U-%u", tp, utc));
+  EXPECT_EQ("2017-00-0", format("%Y-%W-%w", tp, utc));
+
+  tp = convert(civil_second(2017, 12, 31, 0, 0, 0), utc);
+  EXPECT_EQ("2017-53-7", format("%Y-%U-%u", tp, utc));
+  EXPECT_EQ("2017-52-0", format("%Y-%W-%w", tp, utc));
+
+  tp = convert(civil_second(2018, 1, 1, 0, 0, 0), utc);
+  EXPECT_EQ("2018-00-1", format("%Y-%U-%u", tp, utc));
+  EXPECT_EQ("2018-01-1", format("%Y-%W-%w", tp, utc));
+
+  tp = convert(civil_second(2018, 12, 31, 0, 0, 0), utc);
+  EXPECT_EQ("2018-52-1", format("%Y-%U-%u", tp, utc));
+  EXPECT_EQ("2018-53-1", format("%Y-%W-%w", tp, utc));
+
+  tp = convert(civil_second(2019, 1, 1, 0, 0, 0), utc);
+  EXPECT_EQ("2019-00-2", format("%Y-%U-%u", tp, utc));
+  EXPECT_EQ("2019-00-2", format("%Y-%W-%w", tp, utc));
+
+  tp = convert(civil_second(2019, 12, 31, 0, 0, 0), utc);
+  EXPECT_EQ("2019-52-2", format("%Y-%U-%u", tp, utc));
+  EXPECT_EQ("2019-52-2", format("%Y-%W-%w", tp, utc));
+}
+
 //
 // Testing parse()
 //
@@ -1379,10 +1407,80 @@ TEST(Parse, RFC3339Format) {
   EXPECT_TRUE(parse(RFC3339_sec, "2014-02-12T20:21:00+00:00", tz, &tp));
   ExpectTime(tp, tz, 2014, 2, 12, 20, 21, 0, 0, false, "UTC");
 
-  // Check that %Ez also accepts "Z" as a synonym for "+00:00".
+  // Check that %ET also accepts "t".
   time_point<chrono::nanoseconds> tp2;
-  EXPECT_TRUE(parse(RFC3339_sec, "2014-02-12T20:21:00Z", tz, &tp2));
+  EXPECT_TRUE(parse(RFC3339_sec, "2014-02-12t20:21:00+00:00", tz, &tp2));
   EXPECT_EQ(tp, tp2);
+
+  // Check that %Ez also accepts "Z" as a synonym for "+00:00".
+  time_point<chrono::nanoseconds> tp3;
+  EXPECT_TRUE(parse(RFC3339_sec, "2014-02-12T20:21:00Z", tz, &tp3));
+  EXPECT_EQ(tp, tp3);
+
+  // Check that %Ez also accepts "z" as a synonym for "+00:00".
+  time_point<chrono::nanoseconds> tp4;
+  EXPECT_TRUE(parse(RFC3339_sec, "2014-02-12T20:21:00z", tz, &tp4));
+  EXPECT_EQ(tp, tp4);
+}
+
+TEST(Parse, Week) {
+  const time_zone utc = utc_time_zone();
+  time_point<absl::time_internal::cctz::seconds> tp;
+
+  auto exp = convert(civil_second(2017, 1, 1, 0, 0, 0), utc);
+  EXPECT_TRUE(parse("%Y-%U-%u", "2017-01-7", utc, &tp));
+  EXPECT_EQ(exp, tp);
+  EXPECT_TRUE(parse("%Y-%W-%w", "2017-00-0", utc, &tp));
+  EXPECT_EQ(exp, tp);
+
+  exp = convert(civil_second(2017, 12, 31, 0, 0, 0), utc);
+  EXPECT_TRUE(parse("%Y-%U-%u", "2017-53-7", utc, &tp));
+  EXPECT_EQ(exp, tp);
+  EXPECT_TRUE(parse("%Y-%W-%w", "2017-52-0", utc, &tp));
+  EXPECT_EQ(exp, tp);
+
+  exp = convert(civil_second(2018, 1, 1, 0, 0, 0), utc);
+  EXPECT_TRUE(parse("%Y-%U-%u", "2018-00-1", utc, &tp));
+  EXPECT_EQ(exp, tp);
+  EXPECT_TRUE(parse("%Y-%W-%w", "2018-01-1", utc, &tp));
+  EXPECT_EQ(exp, tp);
+
+  exp = convert(civil_second(2018, 12, 31, 0, 0, 0), utc);
+  EXPECT_TRUE(parse("%Y-%U-%u", "2018-52-1", utc, &tp));
+  EXPECT_EQ(exp, tp);
+  EXPECT_TRUE(parse("%Y-%W-%w", "2018-53-1", utc, &tp));
+  EXPECT_EQ(exp, tp);
+
+  exp = convert(civil_second(2019, 1, 1, 0, 0, 0), utc);
+  EXPECT_TRUE(parse("%Y-%U-%u", "2019-00-2", utc, &tp));
+  EXPECT_EQ(exp, tp);
+  EXPECT_TRUE(parse("%Y-%W-%w", "2019-00-2", utc, &tp));
+  EXPECT_EQ(exp, tp);
+
+  exp = convert(civil_second(2019, 12, 31, 0, 0, 0), utc);
+  EXPECT_TRUE(parse("%Y-%U-%u", "2019-52-2", utc, &tp));
+  EXPECT_EQ(exp, tp);
+  EXPECT_TRUE(parse("%Y-%W-%w", "2019-52-2", utc, &tp));
+  EXPECT_EQ(exp, tp);
+}
+
+TEST(Parse, WeekYearShift) {
+  // %U/%W conversions with week values in {0, 52, 53} can slip
+  // into the previous/following calendar years.
+  const time_zone utc = utc_time_zone();
+  time_point<absl::time_internal::cctz::seconds> tp;
+
+  auto exp = convert(civil_second(2019, 12, 31, 0, 0, 0), utc);
+  EXPECT_TRUE(parse("%Y-%U-%u", "2020-00-2", utc, &tp));
+  EXPECT_EQ(exp, tp);
+  EXPECT_TRUE(parse("%Y-%W-%w", "2020-00-2", utc, &tp));
+  EXPECT_EQ(exp, tp);
+
+  exp = convert(civil_second(2021, 1, 1, 0, 0, 0), utc);
+  EXPECT_TRUE(parse("%Y-%U-%u", "2020-52-5", utc, &tp));
+  EXPECT_EQ(exp, tp);
+  EXPECT_TRUE(parse("%Y-%W-%w", "2020-52-5", utc, &tp));
+  EXPECT_EQ(exp, tp);
 }
 
 TEST(Parse, MaxRange) {
diff --git a/third_party/abseil_cpp/absl/time/internal/cctz/src/time_zone_impl.cc b/third_party/abseil_cpp/absl/time/internal/cctz/src/time_zone_impl.cc
index 030ae0e19e07..f34e3aec84d6 100644
--- a/third_party/abseil_cpp/absl/time/internal/cctz/src/time_zone_impl.cc
+++ b/third_party/abseil_cpp/absl/time/internal/cctz/src/time_zone_impl.cc
@@ -15,6 +15,7 @@
 #include "time_zone_impl.h"
 
 #include <deque>
+#include <memory>
 #include <mutex>
 #include <string>
 #include <unordered_map>
@@ -48,17 +49,16 @@ std::mutex& TimeZoneMutex() {
 time_zone time_zone::Impl::UTC() { return time_zone(UTCImpl()); }
 
 bool time_zone::Impl::LoadTimeZone(const std::string& name, time_zone* tz) {
-  const time_zone::Impl* const utc_impl = UTCImpl();
+  const Impl* const utc_impl = UTCImpl();
 
-  // First check for UTC (which is never a key in time_zone_map).
+  // Check for UTC (which is never a key in time_zone_map).
   auto offset = seconds::zero();
   if (FixedOffsetFromName(name, &offset) && offset == seconds::zero()) {
     *tz = time_zone(utc_impl);
     return true;
   }
 
-  // Then check, under a shared lock, whether the time zone has already
-  // been loaded. This is the common path. TODO: Move to shared_mutex.
+  // Check whether the time zone has already been loaded.
   {
     std::lock_guard<std::mutex> lock(TimeZoneMutex());
     if (time_zone_map != nullptr) {
@@ -70,20 +70,15 @@ bool time_zone::Impl::LoadTimeZone(const std::string& name, time_zone* tz) {
     }
   }
 
-  // Now check again, under an exclusive lock.
+  // Load the new time zone (outside the lock).
+  std::unique_ptr<const Impl> new_impl(new Impl(name));
+
+  // Add the new time zone to the map.
   std::lock_guard<std::mutex> lock(TimeZoneMutex());
   if (time_zone_map == nullptr) time_zone_map = new TimeZoneImplByName;
   const Impl*& impl = (*time_zone_map)[name];
-  if (impl == nullptr) {
-    // The first thread in loads the new time zone.
-    Impl* new_impl = new Impl(name);
-    new_impl->zone_ = TimeZoneIf::Load(new_impl->name_);
-    if (new_impl->zone_ == nullptr) {
-      delete new_impl;  // free the nascent Impl
-      impl = utc_impl;  // and fallback to UTC
-    } else {
-      impl = new_impl;  // install new time zone
-    }
+  if (impl == nullptr) {  // this thread won any load race
+    impl = new_impl->zone_ ? new_impl.release() : utc_impl;
   }
   *tz = time_zone(impl);
   return impl != utc_impl;
@@ -104,14 +99,11 @@ void time_zone::Impl::ClearTimeZoneMapTestOnly() {
   }
 }
 
-time_zone::Impl::Impl(const std::string& name) : name_(name) {}
+time_zone::Impl::Impl(const std::string& name)
+    : name_(name), zone_(TimeZoneIf::Load(name_)) {}
 
 const time_zone::Impl* time_zone::Impl::UTCImpl() {
-  static Impl* utc_impl = [] {
-    Impl* impl = new Impl("UTC");
-    impl->zone_ = TimeZoneIf::Load(impl->name_);  // never fails
-    return impl;
-  }();
+  static const Impl* utc_impl = new Impl("UTC");  // never fails
   return utc_impl;
 }
 
diff --git a/third_party/abseil_cpp/absl/time/internal/cctz/src/time_zone_lookup_test.cc b/third_party/abseil_cpp/absl/time/internal/cctz/src/time_zone_lookup_test.cc
index 0b0c1a3b72c6..8f7ab154fade 100644
--- a/third_party/abseil_cpp/absl/time/internal/cctz/src/time_zone_lookup_test.cc
+++ b/third_party/abseil_cpp/absl/time/internal/cctz/src/time_zone_lookup_test.cc
@@ -933,7 +933,7 @@ TEST(MakeTime, Normalization) {
 
 // NOTE: Run this with -ftrapv to detect overflow problems.
 TEST(MakeTime, SysSecondsLimits) {
-  const char RFC3339[] = "%Y-%m-%dT%H:%M:%S%Ez";
+  const char RFC3339[] = "%Y-%m-%d%ET%H:%M:%S%Ez";
   const time_zone utc = utc_time_zone();
   const time_zone east = fixed_time_zone(chrono::hours(14));
   const time_zone west = fixed_time_zone(-chrono::hours(14));
diff --git a/third_party/abseil_cpp/absl/time/internal/cctz/src/zone_info_source.cc b/third_party/abseil_cpp/absl/time/internal/cctz/src/zone_info_source.cc
index 98ea16126782..72095339c3c1 100644
--- a/third_party/abseil_cpp/absl/time/internal/cctz/src/zone_info_source.cc
+++ b/third_party/abseil_cpp/absl/time/internal/cctz/src/zone_info_source.cc
@@ -83,7 +83,8 @@ ZoneInfoSourceFactory default_factory = DefaultFactory;
     "@@U?$default_delete@VZoneInfoSource@cctz@time_internal@" ABSL_INTERNAL_MANGLED_NS                                   \
     "@@@std@@@std@@ABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@2@@Z@" ABSL_INTERNAL_MANGLED_BACKREFERENCE \
     "@@ZA")
-#elif defined(_M_IA_64) || defined(_M_AMD64) || defined(_M_ARM64)
+#elif defined(_M_IA_64) || defined(_M_AMD64) || defined(_M_ARM) || \
+    defined(_M_ARM64)
 #pragma comment(                                                                                                          \
     linker,                                                                                                               \
     "/alternatename:?zone_info_source_factory@cctz_extension@time_internal@" ABSL_INTERNAL_MANGLED_NS                     \
diff --git a/third_party/abseil_cpp/absl/time/time.h b/third_party/abseil_cpp/absl/time/time.h
index b456a13e8505..37f6131dd882 100644
--- a/third_party/abseil_cpp/absl/time/time.h
+++ b/third_party/abseil_cpp/absl/time/time.h
@@ -1203,18 +1203,15 @@ struct tm ToTM(Time t, TimeZone tz);
 // time with UTC offset.  Also note the use of "%Y": RFC3339 mandates that
 // years have exactly four digits, but we allow them to take their natural
 // width.
-ABSL_DLL extern const char
-    RFC3339_full[];  // %Y-%m-%dT%H:%M:%E*S%Ez
-ABSL_DLL extern const char RFC3339_sec[];  // %Y-%m-%dT%H:%M:%S%Ez
+ABSL_DLL extern const char RFC3339_full[];  // %Y-%m-%d%ET%H:%M:%E*S%Ez
+ABSL_DLL extern const char RFC3339_sec[];   // %Y-%m-%d%ET%H:%M:%S%Ez
 
 // RFC1123_full
 // RFC1123_no_wday
 //
 // FormatTime()/ParseTime() format specifiers for RFC1123 date/time strings.
-ABSL_DLL extern const char
-    RFC1123_full[];  // %a, %d %b %E4Y %H:%M:%S %z
-ABSL_DLL extern const char
-    RFC1123_no_wday[];  // %d %b %E4Y %H:%M:%S %z
+ABSL_DLL extern const char RFC1123_full[];     // %a, %d %b %E4Y %H:%M:%S %z
+ABSL_DLL extern const char RFC1123_no_wday[];  // %d %b %E4Y %H:%M:%S %z
 
 // FormatTime()
 //
@@ -1229,6 +1226,7 @@ ABSL_DLL extern const char
 //   - %E#f - Fractional seconds with # digits of precision
 //   - %E*f - Fractional seconds with full precision (a literal '*')
 //   - %E4Y - Four-character years (-999 ... -001, 0000, 0001 ... 9999)
+//   - %ET  - The RFC3339 "date-time" separator "T"
 //
 // Note that %E0S behaves like %S, and %E0f produces no characters.  In
 // contrast %E*f always produces at least one digit, which may be '0'.
@@ -1271,7 +1269,8 @@ inline std::ostream& operator<<(std::ostream& os, Time t) {
 // returns the corresponding `absl::Time`. Uses strftime()-like formatting
 // options, with the same extensions as FormatTime(), but with the
 // exceptions that %E#S is interpreted as %E*S, and %E#f as %E*f.  %Ez
-// and %E*z also accept the same inputs.
+// and %E*z also accept the same inputs, which (along with %z) includes
+// 'z' and 'Z' as synonyms for +00:00.  %ET accepts either 'T' or 't'.
 //
 // %Y consumes as many numeric characters as it can, so the matching data
 // should always be terminated with a non-numeric.  %E4Y always consumes