Yes, except for those occasions when your Saturday is one of the four federal holidays which falls on a day which floats from year to year (New Year’s Day, Independence Day, Veterans Day, and Christmas Day). In that case Saturday is not counted, but the day on which the holiday might be observed is counted even though government offices and banks are closed and regular mail service is suspended.
Other than the exception for federal holidays, it makes no difference if the bank is closed on Saturday as far as counting the days related to receipt of the Closing Disclosure including the mail box rule.