Doesnt work with PHP 5 (includes Fix)

This function doesn't work with PHP5 to fix it change the line

if(($a_dt == -1) || ($b_dt == -1)))

To

if(($a_dt == -1) || ($b_dt == -1) || ($a_dt == false) || ($b_dt == false))


This is because previous to PHP 5.1.0, the strtotime function would return -1 on failure instead of FALSE so the above makes it work with php4 and php5.

Thanks for Your suggestion.
I've applied the change You submitted.

Best regards,

Alex