At the present time, the Islamic calendar is about one day off every 2570 years with respect to the moon. If the Gregorian calendar were to continue, it would err with respect to the sun only a little less. Although the Gregorian calendar is more accurate than the Julian, it still leads to certain confusion. The irregularity of the calendar month causes constant difficulty in business. Years begin on different days of the week.
Holidays often fall in the middle of the week.
Throughout the years, many plans have been proposed to reform the calendar and do away with much of this irregularity. The Thirteen Month Calendar has been proposed as one solution to calendar problems. It provides for thirteen months of exactly four weeks each. Every year begins on Sunday and ends on Saturday. Any given date during the month always falls on the same day each week.