Filter not behaving as expected

I created a filter on Deals on update_time field. But when I pass it to the v1/deals API to get only the ones with update_time equal or later than ‘2021-05-18 23:59:59’ I get Deals with update_time previous to that. For example 2021-05-18 10:20:00

{‘glue’: ‘and’,
‘conditions’: [{‘glue’: ‘and’,
‘conditions’: [{‘object’: ‘deal’,
‘field_id’: ‘12463’,
‘operator’: ‘>=’,
‘value’: ‘2021-05-18 23:59:59’,
‘extra_value’: None}]},
{‘glue’: ‘or’, ‘conditions’: []}]}

if I change ‘>=’ for ‘>’ I don’t get previous dates but it skips some of the Deals that I should get.
I’m als using sort = “update_time ASC”
Any idea of what could happen?