IsDate function (LotusScript® Language)

Tests the value of an expression to determine whether it is a date/time value.


IsDate ( expr )



Any expression.

Return value

IsDate returns TRUE (-1) if expr is any of the following:

  • A Variant value of DataType 7 (Date/Time)
  • A Variant value of type String, where the string represents a valid date/time value
  • A String value representing a valid date/time value

Otherwise IsDate returns FALSE (0).


A date/time value stored in a Variant is an 8-byte floating-point value. The integer part represents a serial day counted from Jan 1, 100 AD. Valid dates are represented by integers between -657434 (representing Jan 1, 100 AD) and 2958465 (representing Dec 31, 9999 AD). The fractional part represents the time as a fraction of a day, measured from time 00:00:00 (midnight on the previous day). In this representation of date/time values, day 1 is the date December 31, 1899.