I think where a Statute is silent on definition, if not defined in the first part of the statute, the word month is given its ordinary meaning. Read the statute to see what other hints it might provide as to how it would be calculated. A calendar month is different from a business month and obviously a lunar month. A business month is thirty (30) days.
4. calendar month., BALLENTINE'S LAW DICTIONARY, Copyright (c) 2010 LexisNexis ®, a division of Reed Elsevier, plc. A month by the calendar, that is, a month computed, not by counting the days intervening, but by referring to the calendar for a month as it appears therein, without regard to the number of days it may contain. 11 Am J2d B & N § 291; a month according to the calendar rather than a lunar month. 5. business month., BALLENTINE'S LAW DICTIONARY, Copyright (c) 2010 LexisNexis ®, a division of Reed Elsevier, plc. A month of thirty days, as distinguished from the calendar month.