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diff --git a/third_party/abseil-cpp/absl/time/civil_time.cc b/third_party/abseil-cpp/absl/time/civil_time.cc
new file mode 100644
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+++ b/third_party/abseil-cpp/absl/time/civil_time.cc
@@ -0,0 +1,175 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/time/civil_time.h"
+
+#include <cstdlib>
+#include <string>
+
+#include "absl/strings/str_cat.h"
+#include "absl/time/time.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+namespace {
+
+// Since a civil time has a larger year range than absl::Time (64-bit years vs
+// 64-bit seconds, respectively) we normalize years to roughly +/- 400 years
+// around the year 2400, which will produce an equivalent year in a range that
+// absl::Time can handle.
+inline civil_year_t NormalizeYear(civil_year_t year) {
+  return 2400 + year % 400;
+}
+
+// Formats the given CivilSecond according to the given format.
+std::string FormatYearAnd(string_view fmt, CivilSecond cs) {
+  const CivilSecond ncs(NormalizeYear(cs.year()), cs.month(), cs.day(),
+                        cs.hour(), cs.minute(), cs.second());
+  const TimeZone utc = UTCTimeZone();
+  // TODO(absl-team): Avoid conversion of fmt std::string.
+  return StrCat(cs.year(),
+                FormatTime(std::string(fmt), FromCivil(ncs, utc), utc));
+}
+
+template <typename CivilT>
+bool ParseYearAnd(string_view fmt, string_view s, CivilT* c) {
+  // Civil times support a larger year range than absl::Time, so we need to
+  // parse the year separately, normalize it, then use absl::ParseTime on the
+  // normalized std::string.
+  const std::string ss = std::string(s);  // TODO(absl-team): Avoid conversion.
+  const char* const np = ss.c_str();
+  char* endp;
+  errno = 0;
+  const civil_year_t y =
+      std::strtoll(np, &endp, 10);  // NOLINT(runtime/deprecated_fn)
+  if (endp == np || errno == ERANGE) return false;
+  const std::string norm = StrCat(NormalizeYear(y), endp);
+
+  const TimeZone utc = UTCTimeZone();
+  Time t;
+  if (ParseTime(StrCat("%Y", fmt), norm, utc, &t, nullptr)) {
+    const auto cs = ToCivilSecond(t, utc);
+    *c = CivilT(y, cs.month(), cs.day(), cs.hour(), cs.minute(), cs.second());
+    return true;
+  }
+
+  return false;
+}
+
+// Tries to parse the type as a CivilT1, but then assigns the result to the
+// argument of type CivilT2.
+template <typename CivilT1, typename CivilT2>
+bool ParseAs(string_view s, CivilT2* c) {
+  CivilT1 t1;
+  if (ParseCivilTime(s, &t1)) {
+    *c = CivilT2(t1);
+    return true;
+  }
+  return false;
+}
+
+template <typename CivilT>
+bool ParseLenient(string_view s, CivilT* c) {
+  // A fastpath for when the given std::string data parses exactly into the given
+  // type T (e.g., s="YYYY-MM-DD" and CivilT=CivilDay).
+  if (ParseCivilTime(s, c)) return true;
+  // Try parsing as each of the 6 types, trying the most common types first
+  // (based on csearch results).
+  if (ParseAs<CivilDay>(s, c)) return true;
+  if (ParseAs<CivilSecond>(s, c)) return true;
+  if (ParseAs<CivilHour>(s, c)) return true;
+  if (ParseAs<CivilMonth>(s, c)) return true;
+  if (ParseAs<CivilMinute>(s, c)) return true;
+  if (ParseAs<CivilYear>(s, c)) return true;
+  return false;
+}
+}  // namespace
+
+std::string FormatCivilTime(CivilSecond c) {
+  return FormatYearAnd("-%m-%dT%H:%M:%S", c);
+}
+std::string FormatCivilTime(CivilMinute c) {
+  return FormatYearAnd("-%m-%dT%H:%M", c);
+}
+std::string FormatCivilTime(CivilHour c) {
+  return FormatYearAnd("-%m-%dT%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);
+}
+bool ParseCivilTime(string_view s, CivilMinute* c) {
+  return ParseYearAnd("-%m-%dT%H:%M", s, c);
+}
+bool ParseCivilTime(string_view s, CivilHour* c) {
+  return ParseYearAnd("-%m-%dT%H", s, c);
+}
+bool ParseCivilTime(string_view s, CivilDay* c) {
+  return ParseYearAnd("-%m-%d", s, c);
+}
+bool ParseCivilTime(string_view s, CivilMonth* c) {
+  return ParseYearAnd("-%m", s, c);
+}
+bool ParseCivilTime(string_view s, CivilYear* c) {
+  return ParseYearAnd("", s, c);
+}
+
+bool ParseLenientCivilTime(string_view s, CivilSecond* c) {
+  return ParseLenient(s, c);
+}
+bool ParseLenientCivilTime(string_view s, CivilMinute* c) {
+  return ParseLenient(s, c);
+}
+bool ParseLenientCivilTime(string_view s, CivilHour* c) {
+  return ParseLenient(s, c);
+}
+bool ParseLenientCivilTime(string_view s, CivilDay* c) {
+  return ParseLenient(s, c);
+}
+bool ParseLenientCivilTime(string_view s, CivilMonth* c) {
+  return ParseLenient(s, c);
+}
+bool ParseLenientCivilTime(string_view s, CivilYear* c) {
+  return ParseLenient(s, c);
+}
+
+namespace time_internal {
+
+std::ostream& operator<<(std::ostream& os, CivilYear y) {
+  return os << FormatCivilTime(y);
+}
+std::ostream& operator<<(std::ostream& os, CivilMonth m) {
+  return os << FormatCivilTime(m);
+}
+std::ostream& operator<<(std::ostream& os, CivilDay d) {
+  return os << FormatCivilTime(d);
+}
+std::ostream& operator<<(std::ostream& os, CivilHour h) {
+  return os << FormatCivilTime(h);
+}
+std::ostream& operator<<(std::ostream& os, CivilMinute m) {
+  return os << FormatCivilTime(m);
+}
+std::ostream& operator<<(std::ostream& os, CivilSecond s) {
+  return os << FormatCivilTime(s);
+}
+
+}  // namespace time_internal
+
+ABSL_NAMESPACE_END
+}  // namespace absl