sacred calendar

The Bible regularly refers to a calendar. It mentions months by number, and sometimes by name. It gives the dates in the relevant months on which the feasts, which God prescribed, had to be held. And then, of course, the unbroken pattern of six days’ work and the seventh day rest underlies all the reckoning of time, just as does the cycle of night and day and the seasons of the year. Even at the time of the deluge, exact dates were given for when the rain began and for when Noah disembarked a year later. And we see that even Noah counted the days in sevens.

What sort of calendar was it?