13 times 28 days = 364 days + 1 Day out of Time = 365 days. This is the simple and clear mathematical elegance and perfection of Nature. The 13-Month, 28-Day Calendar is a LUNAR~SOLAR calendar, not a lunar calendar. Lunar calendars are based on lunations/phases of the moon, and are independent of the solar year. A solar year is the time the Earth takes to orbit the Sun. The 13-Moon/Month, 28 day is a lunar~solar~galactic calendar. It is based on the number of orbits of the moon around Earth in one solar year. The beginning of the year corresponds to the heliacal rising of Sirius ( July 26th on the gregorian calendar )