Hi @Anonymous,
Have your solved your problem?
Do you want to compare the DatePicker selected date with the existing date in your SP list?
Could you please share a bit more about the scenario?
From the screenshot you provided, I think you have a start date column and a end date column, also DatePickers for start date and end date. If so, I think you could compare the selected date with
Please try the following formula
If(
ThisItem.startD <= DatePicker2.SelectedDate && DatePicker2.SelectedDate <= ThisItem.endD ||
ThisItem.startD <= DatePicker3.SelectedDate && DatePicker3.SelectedDate <= ThisItem.endD,
"reserved",
"free"
)
Note that you could only compare the current selected date with the date from the current record.

If this could not solve your problem, please post your solution that works on your side, so that our users could get help form here.
Regards,
Qi