Almost all of the initial calendars were based on the moon's cycles.
Most of them were created locally in different cities and were based on observations regarding the moon's phases.
Every complete cycle was treated as a single month.
Even then various months had different number of days.
The reason was the moon's phases did not line up correctly with night and day cycle of Earth.
A lot of efforts were spared in putting in place the exact number of days inside each month.
Another reason was that many religious celebrations had to be held on specific days and times.
As these cities grew in size and started to become civilizations, civil administrators felt the need for consistent calendars like we have in 2011 calendar or 2010 Calendar.
The solar cycle instead of a lunar one reflected seasonal changes more accurately.
They were anchored by equinoxes and solstices.
The earlier lunar calendars became somewhat more complex lunisolar calendars.
Several societies still rely on lunar calendars that are relatively easier to calculate and judge.
The most notable example is the Muslim calendar.
Mohammed the Prophet rejected the older Arabic calendar which was lunisolar and was in favor of a lunar calendar.
The moon and the Sun however were not the only influenced astronomically on calendars.
There were also other influences such as stars in the sky at night, constellations, planets as well as wandering stars.
They also played a part in influencing calendars.
The constellations however had a more symbolic influence and they kept changing their position in the sky at nights in accordance with a solar year.
All this led to the birth of the astronomy science.