$sType One of the following:
D = Difference in days between the given dates
M = Difference in months between the given dates
Y = Difference in years between the given dates
w = Difference in Weeks between the given dates
h = Difference in hours between the given dates
n = Difference in minutes between the given dates
s = Difference in seconds between the given dates
$sStartDate Input Start date in the format "YYYY/MM/DD[ HH:MM:SS]"
$sEndDate Input End date in the format "YYYY/MM/DD[ HH:MM:SS]"
Return Value
Success: Difference between the 2 dates.
Failure: Returns 0 and set @error
@error: 0 - No error
1 - Invalid $sType
2 - Invalid $sStartDate
3 - Invalid $sEndDate