/**
* date_time_subtract
* same as date_time_add except subtracting value instead of adding.
*
* @param \EE_Base_Class $obj
* @param string $datetime_field_name name of the EE_Datetime_Filed datatype db column to be manipulated
* @param string $period
* @param int $value
* @return \EE_Base_Class
*/
public static function date_time_subtract(EE_Base_Class $obj, $datetime_field_name, $period = 'years', $value = 1)
{
//get the raw UTC date
$DateTime = $obj->get_DateTime_object($datetime_field_name);
$DateTime = EEH_DTT_Helper::calc_date($DateTime, $period, $value, '-');
return EEH_DTT_Helper::_set_date_time_field($obj, $DateTime, $datetime_field_name);
}
