Dim Value As Date
A Date type is represented internally as a signed 64 bit floating point data type with the value to the left of the decimal representing the number of days from the epoch date of December 30th, 1899 (although see the note below). The value to the right of the decimal represents the time as a fractional day. Thus, an integer Date would have a time component of 12:00:00AM and x.5 would have a time component of 12:00:00PM.
Valid values for Dates are between January 1st 100 and December 31st 9999. Since a Double has a larger range, it is possible to overflow a Date by assigning values outside of that range.
As such, it can be used interchangeably with a Double for Date calculations:
Dim MyDate As Double MyDate = 0 'Epoch date. Debug.Print Format$(MyDate, "yyyy-mm-dd") 'Prints 1899-12-30. MyDate = MyDate + 365 Debug.Print Format$(MyDate, "yyyy-mm-dd") 'Prints 1900-12-30.
The casting function to convert to a Date is
CDate(), which accepts any numeric type string date/time representation. It is important to note that string representations of dates will be converted based on the current locale setting in use, so direct casts should be avoided if the code is meant to be portable.