When Was A Calendar Invented. The lunisolar calendar, in which months are lunar but years are solar—that is, are brought into line with the course of the sun—was used. He told astronomers to fix the calendar to line.

The calendar was originally invented by pope gregory xiii, from whom it gets its name. 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.