When Calendar Invented. This is the calendar that has 12 months and 365 cays. One of the earliest known calendars was developed by the babylonians.
The earliest evidence of astronomical activity is an ishango bone with markings, thought to be a lunar calendar which dates back to around 20,000 bc. The earliest calendars date back to the bronze age with civilisations in the near east region, such as the babylonians and persians, being among the first to record time by using natural cycles.