We have an Issue with DST(EDT/EST) when we are trying to save Date as Date Time in PEGA. For example when we are in EDT, we will convert 1/1/2017 as 20170101T050000.000 GMT and when we are in EST, we will convert 1/1/2017 as 20170101T040000.000 GMT. When try to match a Code Group with effective from 1/1/2017 EDT now (IN EST), it will not match as 20170101T040000.000 is 1 hour ahead of 20170101T050000.000 GMT. And if we save the Date Time with 1/1/2017 EST now, then when we go to EDT it will be display as 12/31/2016.
***Edited by Moderator Marissa to update platform capability tags****
I'm not sure I understand what your expectations are. This is generally why it's challenging to turn a date into a datetime. You have to make assumptions and if they are wrong, you need to code around them. Everything you describe could be exactly what someone wants for a different use case. 20170101T040000.000 GMT is rightly 12/31/2016 in EST. Of course, you shouldn't be using EDT on 1/1/2017, because that's not during daylight savings time. It's not recommended to use the three character time zone codes anyway, and using something like America/New_York will manage daylight savings for you in the eastern time zone.
If you are using a date value and ultimately care about the date only, you are better off keeping the property in date format and not datetime, since that will completely avoid issues with time zones and daylight savings.