Hello,
So there is a difference in time zone you save your data, In Reactive or mobile apps server date time converted to local date-time automatically. If you keep the same date time on the client-side between the server-side if you want to convert this, you have to convert date-time fields to text fields. to prevent auto converting function this way.(but i think this is not a best way)
The standard behaviour for reactive web apps to show datetime data in the timezone of client side(users device), and to store them in the timezone of the server. so this is normal.
You can check here we already have thread
https://www.outsystems.com/forums/discussion/73253/datetimecolumn-shows-two-hour-difference-ingrid/
https://www.outsystems.com/forums/discussion/75279/date-time-in-entity-and-ui-screen-different/
https://www.outsystems.com/forums/discussion/75279/date-time-in-entity-and-ui-screen-different/
https://www.outsystems.com/forums/discussion/69618/reactive-app-disable-showing-dates-in-client-timezone/