Circles and PiConstellations

Of course, there are actually 365 days in one year (well, 365.242199 to be exact), but Babylonian mathematicians worked with simple sundials, and this approximation was perfectly adequate.

It also worked well with their existing base-60 number system (since 6×60=360). This system is the reason why we still have 60 seconds in a minute and 60 minutes in an hour – even though most other units are measured in base 10 (e.g. 10 years in a decade, or 100 years in a century).