What form is the date stored in the prefilter?
If you choose a field of type Date, then in Y-m-d or in Y-m-d H:i.
What if the rows part uses the date-time, and you have to choose by date?
There are several approaches:
Create a technical field in the row part, where through dateFormat transform to Y-m-d.
Do not bind the prefilter field in which the date is selected to the row part, but make two hidden prefilter fields with parameters interval. Bind them to the date-time in the row part, and calculate the value in them with code:
For the start:
=: dateFormat(date: #fl_date; format: "Y-m-d 00:00")
For the end:
=: dateFormat(date: #fl_date; format: "Y-m-d 23:59")
The comparison of the start and end goes by the principle of greater/less or equal — the extreme values are included in the interval.
Как быть если надо выбирать по месяцу?
Similarly, through the technical field in the lowercase part or through two interval technical fields of the prefilter:
For the starting one:
=: dateFormat(date: #fl_date; format: "Y-m-01")
For the ending one:
=: dateAdd(date: #fl_teh_start; days: $days)
days: dateFormat(date: #fl_teh_start; format: "t") - 1
// Here we find the last day of the month by the first one