Edited sentence: , the Islamic calendar, or a lunar-solar calendar, e., the Jewish calendar.Apparently, the designers of the calendar were unaware of the possibility of the superior lunar-solar calendar as it is not mentioned in their proposals which nevertheless heap much criticism on previous calendars.The months in the calendar have no natural significance and are purely artificial, as opposed to a lunar calendar, e.This is even more surprising as the calendar was later approved by the great astronomer Lagrange who had studied the motion of the Moon in depth