Years divisible by 400 still retained the extra day.Since its introduction, the difference between the Gregorian calendar (the current "standard" calendar) and the Julian calendar has increased three days every four centuries, corresponding to the dropped leap days for three of the years ending in "00." For years between 19, the difference between the two stands at 13 days.Note that the time scale that is the basis for Julian dates is Universal Time, and that 0h UT corresponds to a Julian date fraction of 0.5.
However, adoption of the Gregorian calendar in the rest of the world progressed slowly. Seidelmann eds., (Mill Valley, CA: University Science Books), Chapter 15, pp. The modified Julian date (MJD) is related to the Julian date (JD) by the formula: MJD = JD - 2400000.5 This data service uses one of our new Application Programming Interfaces (APIs). For further information on calendars, see Richards, E. Julian dates are a continuous count of days and fractions since noon Universal Time on January 1, 4713 BC. But, the Battle of Borodino was fought on 7 September 1812.Thus, there is a ten-day gap in calendar dates, but no discontinuity in Julian dates or days of the week: 4 October 1582 (Julian) is a Thursday, which begins at JD 2299159.5; and 15 October 1582 (Gregorian) is a Friday, which begins at JD 2299160.5.The omission of ten days of calendar dates was necessitated by the astronomical error built up by the Julian calendar over its many centuries of use, due to its too-frequent leap years.