# DATETONUMBER

Use DATETONUMBER to perform arithmetic on dates.

The DATETONUMBER function returns an integer that results from counting the number of days from December 31, 1864, to the specified date.

- Syntax:
- DATETONUMBER (single-date-expression)
- Meaning:
- DATETONUMBER (date_to_convert)
- Returns:
- A single integer

The DATETONUMBER function converts a date to an integer. The resulting integer represents the number of days since December 31, 1864, where using DATETONUMBER with a date of January 1, 1865 returns the integer value 1.

If the input argument is in error, the function returns the value "none".

If the date format specified by the input argument does not
include century, the century is determined based on the **Century** map
setting using the **CCLookup** parameter or the current century.

## Examples

- DaysBetween = DATETONUMBER ( StopDate
) - DATETONUMBER ( StartDate )
This expression could be used in a map rule to produce a value for

**DaysBetween**. It converts the**StopDate**and the**StartDate**to integers, then subtracts the resulting two integers, and returns the result as**DaysBetween**.

## Related functions

- ADDDAYS
- NUMBERTODATE