Seems to be a bug IMHO.
Created an entity with a date time (localized) attribute. Timezone in the setting is None.
Added the attribute in a search field with the option smaller or equal on a datagrid.
Entered 2 values: 24/12/2020 12:00 and 24/12/2020 10:00
When searching on 23/12/2020 11:00 this should yield no results as both entries have a date time after the datetime being search for in the smaller or equal field. This however yields 1 record: 24/12/2020 10:00
Changing the input for the search to 23/12/2020 13:00 returns both records.
Searching on 24/12/2020 11:00 will return both records as well, this should only retrun the record at 10:00.
Searching on 22/12/2020 11:00 will retrun no results as expected and when using the 25th as date will return both records as expected as well.
Changing the server timezone to GMT+01:00 has the same effect as desribed above
Suggest to file a ticket with Mendix support as this comparison function seems to be a bit buggy.