diff --git a/Pkg.Json.Mapper.pas b/Pkg.Json.Mapper.pas
index 641e6fc..6d89f54 100644
--- a/Pkg.Json.Mapper.pas
+++ b/Pkg.Json.Mapper.pas
@@ -441,7 +441,7 @@ function TPkgJsonMapper.GetJsonType(AJsonValue: TJsonValue): TJsonType;
             if AJsonValue is TJSONString then
             begin
               LJsonString := (AJsonValue as TJSONString);
-              if TRegEx.IsMatch(LJsonString.Value, '^([0-9]{4})-?(1[0-2]|0[1-9])-?(3[01]|0[1-9]|[12][0-9])(T| )(2[0-3]|[01][0-9]):?([0-5][0-9]):?([0-5][0-9])$') then
+              if TRegEx.IsMatch(LJsonString.Value, '^(-?(?:[1-9][0-9]*)?[0-9]{4})-(1[0-2]|0[1-9])-(3[01]|0[1-9]|[12][0-9])T(2[0-3]|[01][0-9]):([0-5][0-9]):([0-5][0-9])(\.[0-9]+)?(Z|[+-](?:2[0-3]|[01][0-9]):[0-5][0-9])?$') then
                 result := jtDateTime
               else
                 if TRegEx.IsMatch(LJsonString.Value, '^([0-9]{4})(-?)(1[0-2]|0[1-9])\2(3[01]|0[1-9]|[12][0-9])$') then