Formula to check if it is a Date
If your "date" in cell A1 is a text string and you want to check that it is valid, e.g.:
'30 June 2012 is a valid date
'31 June 2012 is NOT a valid date
you can use:
Try:
=NOT(ISERR(DATEVALUE(A1)))
DATEVALUE returns a date serial number from a text date. If it can't it returns an error which is detected by ISERR. The NOT function then reverses the result so your function returns TRUE if the string CAN be converted to a date.
This can all be shortened by using:
=ISNUMBER(DATEVALUE(A1))
