Many people do not realize that God has instituted a way of telling time, a calendar. Today we use the Gregorian calendar, where many of the months and all of the days of the week are named after various pagan gods. The Gregorian calendar was instituted by Pope Gregory XIII in 1582. It was used in Europe, in the Catholic nations, and spread around the world from there.
But lets focus on what God has done instead of man.
Then God said, “Let there be lights in the firmament of the heavens to divide the day from the night; and let them be for signs and seasons, and for days and years; (Genesis 1:14)
The word translated as "seasons" in Hebrew is "moed" (mow-ed) (מוֹעֵד) (plural: moedim). It means appointed time or appointed place. God set the lights in the heavens to tell appointed times.
Now the LORD spoke to Moses and Aaron in the land of Egypt, saying, “This month shall be your beginning of months; it shall be the first month of the year to you. (Exodus 12:1-2)
The word for month is "chodesh" (khō'·desh) (חֹדֶשׁ). And it also means "new moon" or "renewed moon", meaning when the sliver of the moon reappears, it is a new month.
This is called the month of the Abib (Hebrew: Aviv, אביב). Abib is not technically its name, (none of the months were given names by God, but were given names later by men). Abib means ripe. It is the month when the barley becomes ripe. This is how God prevents seasonal drift. The Gregorian calendar has leap years for the same reason.
A biblical year normally consists of 12 months, however, every 2-3 years the barley is not ripe on time and a 13th month is added on.
A week still had seven days, based on creation week. None of these days had names either, except the sabbath day.
A day went from sundown to sundown based on the repetitive theme in Genesis 1 of "evening and morning".
Note that the biblical calendar is different, though very similar to the Jewish calendar. The Jews used Gods calendar up until they last of hem where removed from Israel in the fourth century. Since they were no longer going to be in the land to see the signs, Hillel II established a fixed calendar based on mathematical and astronomical calculations and works on a 19 year cycle. It was only meant to be used until the Jews returned to the land, however, today the Jews are back home and they still use this calendar today.
See our calendar for predicted feast dates