Takes all the arguments of calc_recur, followed by a day of the month
to prorate to (which must be <= 28). Calculates a prorated charge from
the $sdate to that day, and sets the $sdate and $param->{months} accordingly.
Takes all the arguments of calc_recur, followed by a day of the month
to prorate to (which must be <= 28). Calculates a prorated charge from
the $sdate to that day, and sets the $sdate and $param->{months} accordingly.