THis has to do with the localization setting of your attribute.
If you are only interested in the date portion of your attribute then set the localization to no.
In your situation the user is entering the date as 31-05-2025 00:00 and this is assumed to be localized and when living in GMT+2:00, due to daylight saving time for example, the date will be converted to UTC (GMT+0:00) so 2 hours are deducted from the time entered. This will not be the case when not using localization of yoour attribute. For more information see: https://docs.mendix.com/refguide/date-and-time-handling/