An introduction to astronomy: designed as a text-book for the use of students in college. By Denison Olmsted ...

THE CALENDAR. 47
of February; and since the year 1731 closed the 25th of
March, while according to new style 1732 would have commenced on the preceding 1st of January; therefore, the time
required is Feb. 22d, 1732. It is usual, in such cases, to write
both years, thus: Feb. 11, 1731-2, 0. S.
2. A great eclipse of the sun happened May 15th, 1836; to
what date would this time correspond in old style
Ans. May 3d.
115. Thee common year begins and ends on the same day of
the weekc; but leap year ends one day later in the week than it
begatn.
For 52 x7=364 days; if, therefore, the year begins on Tuesday, for example, 364 days would complete 52 weeks, and one
day would be left to begin another week, and the following
year would begin on Wednesday. Hence, generally, any day
of the month is one day later in the week than the same day
of the preceding year. Thus, July 4th, 1861, falls on Thursday;
1862, on Friday; 1863, on Saturday. But, in leap-year, thlis
rule applies only till the end of February. From that time to
the same date in the year following, every day of a month
falls two days later in the week than during the previous year.
Thus, July 4th, 1871, is Tuesday; 1872, Thursday; and February 2d, 1872, is Friday; 1873, Sunday.
1 1 6. Fortunately for astronomy, the confusion of dates involved in different calendars affects recorded observations but
little. Remnarkable eclipses, for example, can be calculated
back for several thousand years, without any danger of mistaking the day of their occurrence; and whenever any such
eclipse is so interwoven with the account given by an ancient
author of some historical event, as to indicate precisely the
interval of time between the eclipse and the event, and at the
same time completely to identify the eclipse, that date is recovered and fixed forever.*
O An elaborate view of the Calendar may be found in Delambre's Astronomy,
t. III. A useful table for finding the day of the week of any given date, is inserted in the American Almanac for 1832, p. 72.