They studied predictable cycles in the sky
They used astronomy and the sun dial to make accurate yearly calendars
Most ancient calendars were based off of the Moon's position, the Stars' position, the Sun's position, and the season.
its sixteen miles high.
Wood is a natural resource that has been used since ancient times and so long ago that there were no calendars back then to record it.
Well, the calender that we currently use today by de facto is a Gregorian Calender which was devised in the middle ages; but the Gregorian calender is heavily based on the Julian Calender constructed by Julius Cesar in 45BC.
5,000 years ago
In my opinion, I think the years were longer than they are now 2 billion years ago. No one will really ever know since there is no calendars that have been left behind from 2 billion years ago.
12,000 years ago.
Egyptians people who invented the Multiplication.Babylonians thousands of years ago.
Calendars were invented thousands of years ago. It is divided into days, weeks, and months.
There was actually a Saint Nick. he delivered presents to the people in his town. So, Yes they did celebrate Christmas long ago.
Ozone was created long ago. It was due to this fact humans were able to develop.