diff --git a/Tests/CMakeTests/String-TIMESTAMP-UnixTime.cmake b/Tests/CMakeTests/String-TIMESTAMP-UnixTime.cmake
index a93e7f5467..43c93848e7 100644
--- a/Tests/CMakeTests/String-TIMESTAMP-UnixTime.cmake
+++ b/Tests/CMakeTests/String-TIMESTAMP-UnixTime.cmake
@@ -11,12 +11,12 @@ string(TIMESTAMP days "%j" UTC)
 # see if we are somewhere in the right region.
 
 math(EXPR years_since_epoch "${year} - 1970")
-math(EXPR lower_bound "((${years_since_epoch} * 365) + ${days}) * 86400")
+math(EXPR lower_bound "((${years_since_epoch} * 365) + ${days} - 1) * 86400")
 math(EXPR upper_bound "((${years_since_epoch} * 366) + ${days}) * 86400")
 
 
-if(unix_time GREATER lower_bound AND unix_time LESS upper_bound)
+if(unix_time GREATER_EQUAL lower_bound AND unix_time LESS upper_bound)
   message("~${unix_time}~")
 else()
-  message(FATAL_ERROR "${timestamp} unix time not in expected range [${lower_bound}, ${upper_bound}]")
+  message(FATAL_ERROR "${timestamp} unix time not in expected range [${lower_bound}, ${upper_bound})")
 endif()
diff --git a/Tests/CMakeTests/StringTest.cmake.in b/Tests/CMakeTests/StringTest.cmake.in
index 83655dae5f..566f4b1e20 100644
--- a/Tests/CMakeTests/StringTest.cmake.in
+++ b/Tests/CMakeTests/StringTest.cmake.in
@@ -47,7 +47,7 @@ set(TIMESTAMP-AllSpecifiers-STDERR "~[0-9]+(;[0-9]+)*~")
 set(TIMESTAMP-MonthWeekNames-RESULT 0)
 set(TIMESTAMP-MonthWeekNames-STDERR "~[^%]+;[^%]+~")
 set(TIMESTAMP-UnixTime-RESULT 0)
-set(TIMESTAMP-UnixTime-STDERR "~[1-9][0-9]+~")
+set(TIMESTAMP-UnixTime-STDERR "~[0-9]+~")
 
 include("@CMAKE_CURRENT_SOURCE_DIR@/CheckCMakeTest.cmake")
 check_cmake_test(String