Here is the answer from National:
Thank you for contacting the National Advancement Team regarding how months are counted toward rank advancement requirements.
Your council registrar is correct. Months are calculated as the period of time between the same dates in successive months. They are not calculated as a specific number of weeks or days. Time periods listed in rank and merit badge requirements were specifically written the way they are on purpose. They are not intended to be interpreted to mean something else. If it was intended that the requirement completion be determined using weeks or days, it would have been written that way. In summary:
A month is the period of time between the same dates in successive months.
A week is a period of seven days, but the beginning of the week can be any day of the week.
Days are individual dates (not necessarily a full 24 hours).
For time served in a position of responsibility the requirement was written using months to simplify the process of keeping track of the time spent. It would be too difficult and confusing to use days or weeks instead of months. For example, if a Scout had their First Class board of review on March 15, then the earliest they would be eligible to sit for a Star board of review would be four months later on July 15, assuming all other requirements were completed by then. Likewise, the earliest the Scout would be eligible to sit for their Life board of review would be January 15.
I trust that this answers your question.
Thanks for all you do for Scouting.
Garfield S. Murden | National Director, Scouts BSA
BOY SCOUTS OF AMERICA
Pilots & Program Development
1325 West Walnut Hill Lane | P.O. Box 152079
Irving, Texas 75015-2079
P 972.580.2478
C 214.532.5335
Garfield.Murden@scouting.org
https://www.scouting.org/programs/scouts-bsa/