The genealogy from Adam to the flood is 1656 AM or years from creation (
Genesis 5:1-32). Add 292 years to Abraham's birth or 1948 AM (
Genesis 11:10-32). Abraham was 75 when God made a covenant (
Genesis 12:1-2, 4). There are 430 years from the Abrahamic covenant to Mt. Sinai (
Exodus 12:41,
Galatians 3:17). This includes ~120 years the Hebrews were enslaved in Egypt. The Exodus is 2453 AM. Add 40 years in the wilderness and 5 years conquering the land. There are 480 years from Joshua as judge to Solomon's 4th year (
1 Kings 6:1). Samson, Eli, Samuel, Saul and Philistines overlap. The first temple was built by Solomon in 2978 AM and lasted 410 years through the kings of Judah. In 3388 AM or 586 BC, the temple was destroyed by Babylon (
2 Kings 25:8-9). Add 586 and 2021 then subtract 1. There is no year zero between BC and AD. The 1st of
Tishri (September) is about 5994 AM. That is a good estimate of years from creation. There is a reason we are seeing so much prophecy fulfilled.
Calendars do not match God's time. The
Jewish year 5781 is off by ~216 years. Add 5 years for Abraham, 40 years in the wilderness and 5 years of conquest. Jews count 490 years between destruction of the first and second temples but 586 BC to 70 AD is 656 years. Add 166 missing years for Persian and Greek rules of Judea. The Roman year is off by ~25 years. Most scholars believe Jesus was born before 1 BC. We are in the 21st century but not in the millennial reign of Christ. God's calendar counts from the cross and not Christ's birth. Because of possible calendar issues, allow for a 7 year margin of error.