February By my logic the first two meanings lack of either a full or new moon in a month can only occur in Februray as the lunar cycle is  days and the shortest nonFeburary month is  days  Feburary being  days or  in a bissextile year is the only month that is less than the full cycle and that therefore can miss either a full or new moon in the month  As the cycle from dark moon to dark moon is less than  days it is also impossible to occur outside February  As for the fourth meaning two new moons in a month obviously this cannot occur in February