How to avoid TDateTime Data Rounding

Question

I am writing column and cell classes for FMX TGrid that will contain TCalendarEdit and TTimeEdit instances in every cell. Everything works

Answer 1

TDateTime is of type Double, which means it's a floating point value, and therefore is subject to the usual issues of binary representation when doing comparisons for equality without specifying an acceptable delta (difference)..

Specifically for TDateTime values, you can use DateUtils.SameDateTime to compare equality down to less than one millisecond:

FDate_Time.Modified := (FDate_Time.Modified) or
           (not SameDateTime(FDate_Time.FieldValue, 
            FCalendarEdit.Date + FTimeEdit.Time));