diff --git a/sdk/core/azure-core/src/datetime.cpp b/sdk/core/azure-core/src/datetime.cpp
index 0084fddbe..b9aba28c2 100644
--- a/sdk/core/azure-core/src/datetime.cpp
+++ b/sdk/core/azure-core/src/datetime.cpp
@@ -92,6 +92,11 @@ constexpr ComputeYearResult ComputeYear(int64_t secondsSince1601)
   int secondsInt = static_cast<int>(secondsLeft - static_cast<int64_t>(year4) * SecondsIn4Years);
 
   int year1 = secondsInt / SecondsInYear;
+  if (year1 == 4)
+  {
+    // this is the last day in a leap year
+    year1 = 3;
+  }
   secondsInt -= year1 * SecondsInYear;
 
   return {year400 * 400 + year100 * 100 + year4 * 4 + year1, secondsInt};
diff --git a/sdk/core/azure-core/test/ut/datetime.cpp b/sdk/core/azure-core/test/ut/datetime.cpp
index 8d706caf2..4f49239af 100644
--- a/sdk/core/azure-core/test/ut/datetime.cpp
+++ b/sdk/core/azure-core/test/ut/datetime.cpp
@@ -409,6 +409,13 @@ TEST(DateTime, ParseTimeRfc3339AcceptsLowercaseTZ)
   TestDateTimeRoundtrip("1970-01-01T00:00:00z", "1970-01-01T00:00:00Z");
 }
 
+TEST(DateTime, ParsingTimeRoundtripLeapYearLastDay)
+{
+  TestDateTimeRoundtrip("2016-12-31T20:59:59Z");
+  TestDateTimeRoundtrip("2020-12-31T20:59:59Z");
+  TestDateTimeRoundtrip("2021-01-01T20:59:59Z");
+}
+
 TEST(DateTime, ParseTimeRoundtripAcceptsInvalidNoTrailingTimezone)
 {
   // No digits after the dot, or non-digits. This is not a valid input, but we should not choke on