TCellValue.IsDateTime Method
Returns true if the value is a DateTime. Note::This value will never be true when reading cells from a file. When reading a file, dates are stored as number so they will be returned as numbers. This property only will return true if you manually created a TCellValue from a TDateTime.
To know if a cell has a date, you need to look at its format, not its value.
Syntax
Unit: FlexCel.Core
function TCellValue.IsDateTime: Boolean;