Mont. Code Ann. § 5-2-103

Each regular session of the legislature shall be convened at the seat of government at 12 noon on the first Monday of January of each odd-numbered year or, if January 1 is a Monday, on the first Wednesday. The legislature shall meet at other times when convened by the governor or by the written request of a majority of the legislators or, when the legislature is in session, by a recorded vote of a majority of the legislators.