Returns file time as a DateTime value.
This function can be used to return the pwdLastSet value from AD to convert it from Int64 to DateTime. As this is a nullable int64 you will need to get the value as below:
If you are getting errors due to 0 values then you can combine this expression with an if statement to convert 0 to Null.
IF(EQUALS(pwdLastSet, 0), NULL(), FROMFILETIME(pwdLastSet.Value))