Query builder - GroupBy `unit_id` having equals (or similar +- one second) date

Hi everyone!

Can you help me please? I need to write code for getting records from database grouped by unit_id and similar dates. Collection has these fields: unit_id, report_time, some .. other .. fields.

I need to get all records, but grouped by field unit_id and by report_time, which is equal (or similar +- one second).

Thanks!