The Calendar
The reckoning of time among the ancients was very inaccurate. This was owning to their ignorance of astronomy, and also to changes that were made from time to time for political reasons. The calendar was reformed by Julius Cæsar, 46 B. C., who made the year consist of 3651⁄4 days, adding one day every fourth year. In 1582, the error in the calendar established by him had increased to 10 days; that is, too much time had been reckoned as a year, until the civil year was 10 days behind the solar year. To correct this error, Pope Gregory XIII. decreed that 10 days should be stricken from the calendar, that the day following the 3d day of October, 1582, should be made the 14th, and that henceforth only those centennial years should be leap years which are divisible by 400.
Most Catholic countries adopted the Gregorian Calendar soon after it was established. Great Britain did not adopt it until 1752, when the error amounted to 11 days. By Act of Parliament, the 3d of September was called the [867] 14th. The civil year by the same act was made to commence on the 1st of January, instead of the 25th of March, as was previously the case.
THE COMPARATIVE TIME ZONES OF THE WORLD
Dates reckoned by the Julian calendar are called Old Style (O.S.), and those reckoned by the Gregorian calendar are called New Style (N.S.). The difference now amounts to 12 days.
Perpetual Calendar
To find the day of the week for any given date.
1. Take the last two figures of the year, add one-fourth of them (neglecting remainder). Thus: 1949 = 49 + 12 = 61.
2. Add for the month, if for January or October, 1; May, 2; August, 3; February, March, or November, 4; June, 5; September or December, 6; April or July, 0; if leap year (that is, if it be divisible by 4 without remainder) January 0; February 3.
3. Add day of month.
Divide the sum of these three by 7, and remainder gives the number of the day of the week.
Thus:—What day of the week is 15th July, 1908?
| 1. 8 + 2 | = | 10 | ||
| 2. July | = | 0 | ||
| 3. 15th | = | 15 | ||
| 25 | = | 7 × 3 + 4 | ||
4th day of the week = Wednesday.
What day of the week was December 25th, 1905?
| 1. 5 + 1 | = | 6 | ||
| 2. Dec. | = | 6 | ||
| 3. 25th | = | 25 | ||
| 37 | = | 7 × 5 + 2 | ||
2nd day of the week = Monday.
The above only applies to 20th Century. For 19th Century, add 2; for 21st Century, add 6; 18th Century, 4; but before 1752 the “old style” was used.