diff --git a/http/ut/utility_test.cpp b/http/ut/utility_test.cpp
index fc8b90e..cb914d5 100644
--- a/http/ut/utility_test.cpp
+++ b/http/ut/utility_test.cpp
@@ -61,17 +61,17 @@
 {
     // some time before the epoch
     EXPECT_EQ(crow::utility::getDateTimeStdtime(std::time_t{-1234567}),
-              "1969-12-17T17:03:53Z");
+              "1969-12-17T17:03:53+00:00");
     // epoch
     EXPECT_EQ(crow::utility::getDateTimeStdtime(std::time_t{0}),
-              "1970-01-01T00:00:00Z");
+              "1970-01-01T00:00:00+00:00");
     // some time in the past after the epoch
     EXPECT_EQ(crow::utility::getDateTimeUint(uint64_t{1638312095}),
-              "2021-11-30T22:41:35Z");
+              "2021-11-30T22:41:35+00:00");
     // some time in the future, beyond 2038
     EXPECT_EQ(crow::utility::getDateTimeUint(uint64_t{41638312095}),
-              "3289-06-18T21:48:15Z");
+              "3289-06-18T21:48:15+00:00");
     // the maximum time we support
     EXPECT_EQ(crow::utility::getDateTimeUint(uint64_t{253402300799}),
-              "9999-12-31T23:59:59Z");
+              "9999-12-31T23:59:59+00:00");
 }