359c359,365
<   $num_days_prev = cal_days_in_month(CAL_GREGORIAN, $month-1, $year);
---
> 
>   if($month==1) {
>     $num_days_prev = cal_days_in_month(CAL_GREGORIAN, 12, $prev_year);
>   } else {
>     $num_days_prev = cal_days_in_month(CAL_GREGORIAN, $month-1, $year);
>   }
>