Reform of the Calendar

For the measurement of time the most important units furnished by 
natural phenomena are the Day and the Year. In regard of both, it 
is convenient and usual to speak of the apparent movements of the 
sun and stars as if they were real, and not occasioned by the 
rotation and revolution of the earth. 

The Day is the interval between two successive passages of the sun 
across the meridian of any place. It is commonly computed from the 
midnight passage across the inferior meridian on the opposite side 
of the globe; but by astronomers from the passage at the noon 
following. The Civil Day is thus twelve hours in advance of the 
Astronomical. 

The Solar Day, which is what we always mean by this term day, is 
longer by about four minutes of time than the Sidereal, or the 
successive passages of a fixed star across the same meridian; for, 
owing to the revolution of the earth in its orbit from west to 
east, the sun appears to travel annually in a path (the ecliptic), 
likewise from west to east, among the stars round the entire 
heavens. The belt of constellations through which it appears to 
proceed is styled the zodiac. During half the year (March to 
September) the ecliptic lies to the north of the celestial 
equator; during the other half (September to March) to the south. 
The points where ecliptic and equator intersect are called the 
equinoxes. In the northern hemisphere the March equinox (or "first 
point of Aries") is called the vernal equinox; the September 
equinox ("first point of Libra"), the autumnal. 

The Year (Tropical Year) is the period in which the sun makes a 
complete circuit of the heavens and returns to the point in the 
zodiac whence it started, and the problem to be solved by those 
who construct calendars is to find the exact measure of this 
yearly period in terms of days, for the number of these occupied 
by the sun's annual journey is not exact. Taking the vernal 
equinox as a convenient starting-point, it is found that before 
the sun arrives there again, 365 days and something more have 
passed. These are, of course, solar days; of sidereal days, each 
shorter by four minutes, there are 366. The first attempt to find