Update cctz to 2021-03-11

contrib/libs/cctz/src/time_zone_fixed.cc

@@ -48,7 +48,7 @@ int Parse02d(const char* p) {
 }  // namespace
 
 bool FixedOffsetFromName(const std::string& name, seconds* offset) {
-  if (name.compare(0, std::string::npos, "UTC", 3) == 0) {
+  if (name == "UTC" || name == "UTC0") {
     *offset = seconds::zero();
     return true;
   }

contrib/libs/cctz/test/time_zone_lookup_test.cc

@@ -714,6 +714,18 @@ TEST(TimeZones, LoadZonesConcurrently) {
   EXPECT_LE(failures.size(), max_failures) << testing::PrintToString(failures);
 }
 
+TEST(TimeZone, UTC) {
+  const time_zone utc = utc_time_zone();
+
+  time_zone loaded_utc;
+  EXPECT_TRUE(load_time_zone("UTC", &loaded_utc));
+  EXPECT_EQ(loaded_utc, utc);
+
+  time_zone loaded_utc0;
+  EXPECT_TRUE(load_time_zone("UTC0", &loaded_utc0));
+  EXPECT_EQ(loaded_utc0, utc);
+}
+
 TEST(TimeZone, NamedTimeZones) {
   const time_zone utc = utc_time_zone();
   EXPECT_EQ("UTC", utc.name());