Since the 4th millenium BC it was known that a year consists of 365 days. Furthermore did the year have 5 extra days.
The year began with the raise of Sirius and the flooding of the Nil on the same day. Every 4 years Sirius was one day late since the year has not 365 but 365,25 days.

It took 1460 years until the raise of Sirius and the flooding of the Nil were on the same day again. Through this phenomena the actual year length of 365,25d was found.

For this reason there was one leap day inserted.

At that time the Egyptians already knew many constellations and the signs of the zodiac were known, too. The signs of the zodiac were divided up into 36 so called „deans“. Each dean was for one special god.