J
Jaipur
A famous early 18th century solar astronomical centre in India, constructed by the Maharaja Jai Singh around 1724. It includes many monumental sundials, including a famous equatorial one with a gnomon 27 metres high.
Julian calendar
The calendar system introduced by Emperor Julius Caesar and devised by the Greek philosopher (and court astronomer of Egypt) Sosigenes. Widely used from 45BC to 1582AD. By this date, it was in error (compared to the Earth’s orbit) by 10 days due to the imperfect use of leap years (i.e. it assumed the length of a year was 365.25 days).
Julian Day
That Scaliger named the system after his father.