Calendar

20 Annotations

First Reading

Emilio  •  Link

A couple of very informative postings on the calendar changes between Pepys's time and ours. First why:

The calendar problem was Easter. In the 6th century, the current formula for scheduling Easter was determined — the Sunday after the full moon after the spring equinox. The Julian calendar assumed that the year was 365.25 days long (so every four years had an extra day to keep the calendar was drifting). The formula for Easter assumed that the equinox was on March 21st, which it was, approximately, in the 6th century. It also assumed that that didn't drift. But there aren't 365.25 days in a year, there are (approximately) 365.2422 days between vernal equinoxes, so over 1000 years that extra 11m14s per year added up to about 8 extra days — which meant Easter was in danger of being scheduled incorrectly. This was demonstrated to Pope Gregory, complete with a revised estimate of the length of the year. The solution he accepted was to a) drop a few days from the calendar to bring the equinox back to March 21st, and b) modify the calendar to drop 3 days over the course of every 400 years, adjusting the average length of the year to 365.2425 days (long by 26s/year). Pope Gregory made his change official in 1582, but by that time, Henry VIII had already separated England from the authority of the Pope, and his daughter Elizabeth was on the throne. England saw no need to change its calendar to meet Papal decrees. By 1750, the calendars across the English channel differed by about 10 days, the "official" new years differed by several months (England traditionally changed years on March 25th), and the increasing foreign trade of the time was being hampered by the calendar differences. So Parliament changed the calendar to align it with the Gregorian one. Posted by Buddha Buck on Mon 13 Jan 2003, 9:41 pm

And a site to do the conversion for you (the Help link on the site provides more detail about the date change in England):
http://www.albion.edu/english/cal… Posted by David Quidnunc on Sat 25 Jan 2003, 9:29 pm

Emilio  •  Link

A good site for calculating the phases of the moon for Pepys (also from David Quidnunc): http://sunearth.gsfc.nasa.gov/ecl… The nice thing about the calculations is that they're in Greenwich Mean Time - which covers England. The website above doesn't mention the old style/new style dating problem, so I assume it ignores it. Posted by David Quidnunc on Sat 25 Jan 2003, 9:29 pm

David Quidnunc  •  Link

Leap years

In the diary years, 1660, 1664 and 1668 were leap years. Two entries (for both 28 & 29 Feb.) were posted on 28 February 2003 in order to keep the entry dates the same as the modern calendar dates.

The reverse problem happens in the leap years of 2004, 2008 and 2012. In those years the daily diary entries would have to post no entry on 29 February if we're to keep Pepys's and our dates the same.

PHE  •  Link

Why UK financial year starts 6th April
An interesting explanation of this is linked to the change in calendar systems. The financial year traditonally started at the start of the calendar year - that is on 25th March. When we switched to the Gregorian calendar in 1750 (or there-abouts), we 'lost' about 12 days in order to make up for the shift that had occurred due to the leap year error (explained by Emilio above - although he/she suggests 10 days error). As accountants at that time didn't want to deal with a financial year that was 12 days short, it was extended to the new 6th April (25th March plus 12 days) - and has stayed there ever since.

E  •  Link

The 'lost' twelve days explain why you should not take down your Christmas decorations before Twelfth Night -- "Old Christmas Day".

dirk  •  Link

Calendar conversion

This site allows you to convert Julian (British) dates easily into Gregorian (continental) and vice versa.

I tested it with a couple of known dates, and it seems to work.
http://pdc.ro.nu/mjd.cgi

dirk  •  Link

Calendar conversion - cont'd

For this conversion engine, the year is taken to begin on Jan 1st.

Grahamt  •  Link

If you have access to a Unix or Linux system:
Try typing
cal 9 1752
you should see:
September 1752
Sun Mon Tue Wed Thu Fri Sat
- - 1 2 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
Showing the 12 "lost" days as Britain went from Julian to Gregorian.
(but aligned correctly - the diary software removes extra spaces)

Mike Barnas  •  Link

Small point, Graham, but 3 through 13 inclusive is eleven days, as noted by the unhappy mobs in 1752 who chanted, we are told, "Give back our eleven days!"

dirk  •  Link

For the sake of completeness:

In Sam's time there were - as yet - only 10 lost days. The additional 11th day, which people were so unhappy about in 1752, was the result of the leap day added to february 1700 in the British (Julian) calendar - and NOT in the (corrected) continental, Gregorian calendar.

This means that for example 11 March 1660/1661 was 11 + 10 = 21 March according to the continental calendar. The following day (Gregorian) would then be the 22 March. The difference between this 22 March and the previous day, 11 March (British), is 11 days - but only 10 of these are "lost".
(Wow! Not quite sure that made things any clearer...)

dirk  •  Link

One of the best calendar convertors so far:
(also calculates Easter dates etc.)

http://www.albion.edu/english/cal…

Note: for this calculator the year is taken to begin on 1st January (old style and new style).

dirk  •  Link

Note: this is of course the link in Emilio's first annotation to this page, but updated (Emilio's original link doesn't work any more.)

Neither does the link in Emilio's second annotation (moon phases). Here's an update to that one:

http://sunearth.gsfc.nasa.gov/ecl…

Second Reading

Sasha Clarkson  •  Link

For the whole of Sam's diary, it's quite simple: add 10 days to Sam's dates to find Gregorian dates, and if necessary subtract the total days in this month to find the date next month:

(eg: Julian 23rd January + 10 days = 33rd January, - 31 days = 2nd February Gregorian.)

The previous links to find 17th century moon phases are dead; the current NASA resource is below:

http://eclipse.gsfc.nasa.gov/phas…

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