Whenever any act of a secular nature, other than a work of necessity or mercy, is appointed by law or contract to be performed upon a particular day, which day falls upon a holiday or a Saturday, such act may be performed upon the next business day with the same effect as if it had been performed upon the day appointed.
Postponement Of Day Appointed For An Action When It Falls On A Holiday Or Saturday
Mont. Code Ann. § 1-1-307, under Rules Concerning Time.
Mont. Code Ann. § 1-1-307