Martin Gainty wrote:Alright I'll ask the dumb question What happened on Jan 1 1601??? -Martin
Of most interest to clocks is that by that day, the start of the seventeenth century, most of the western world had updated their calendars to adopt the no-leap-centuries-except-on-millennium rule that kept the wall time more in sync with astronomicial time. So if you ignore dates before 1601 you dont have to worry so much about when different countries skipped a fair few days to catch up.
I'm not sure why Microsoft chose 1601 as their epoch date, but I don't think that it was for this reason. True, 1601 avoids Pope Gregory's purge of 10 days from 1582 which many countries adopted within a few years, but there are many other countries that took decades or centuries to do so, including the country where Microsoft is based. Here are the dates when various countries changed over, from the "ncal" unix program:
AL Albania 1912-11-30 IT Italy 1582-10-04 AT Austria 1583-10-05 JP Japan 1918-12-18 AU Australia 1752-09-02 LI Lithuania 1918-02-01 BE Belgium 1582-12-14 LN Latin 9999-05-31 BG Bulgaria 1916-03-18 LU Luxembourg 1582-12-14 *CA Canada 1752-09-02 LV Latvia 1918-02-01 CH Switzerland 1655-02-28 NL Netherlands 1582-12-14 CN China 1911-12-18 NO Norway 1700-02-18 CZ Czech Republic 1584-01-06 PL Poland 1582-10-04 DE Germany 1700-02-18 PT Portugal 1582-10-04 DK Denmark 1700-02-18 RO Romania 1919-03-31 ES Spain 1582-10-04 RU Russia 1918-01-31 FI Finland 1753-02-17 SI Slovenia 1919-03-04 FR France 1582-12-09 SE Sweden 1753-02-17 GB United Kingdom 1752-09-02 TR Turkey 1926-12-18 GR Greece 1924-03-09 US United States 1752-09-02 HU Hungary 1587-10-21 YU Yugoslavia 1919-03-04 IS Iceland 1700-11-16
Note that only 11 of these 24 countries changed before 1600. You can view the truly weird months for your locale using the "cal" or "ncal" programs. Here is the command if you are in Britain or one of her former colonies:
$ cal 09 1752
(if you are in some other locale, you may need to run "ncal -s GB 09 1752" to see the same thing).
I don't know about other countries, but in England the Calendar Reform Act caused much confusion as landlords expected to be paid a month's rent while tenants had 11 fewer days to earn the money for it. People marched in the streets crying, "Give us back our 11 days!" Then there was the loss of January, February, and most of March from 1752 in England, but that is another story (and one neither the cal nor ncal programs demonstrate, probably because of the UI difficulty in showing a year change in the middle of a month).
I suspect the reason Microsoft chose 1601 is because they had to choose some date, and 1601 captures 99.999% of the dates that are likely to be entered by all but specialist users. Perhaps not coincidentally, I chose the same epoch year once for a program I wrote. Maybe it is some kind of forced choice like, "Pick a number between 1 and 4."
[If you chose a number before reading this, in all likelihood you chose "3"]
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