International Date Line

INTERNATIONAL DATE LINE The 180th meridiar designated the International Date Line by the Internat Meridian Conference in 1884. It was adopted in ord avoid the confusion of the difference of one day travellers would face while travelling across the ~ Counting from Greenwich Meridian, the date immedi east of this line is one day ahead or 12 hours faster in the west.

Though the 180° meridian generally falls the ocean, the International Date Line has had to de both eastward and westward in order to permit CE landmasses and islands to have the same calendar day.

It passes through the Arctic Ocean, Chukchi sea, a, Wrangel Island and Russian landmass, passes thr, Bering Strait, veers again to avoid Aleutian Islands,
through Pacific Ocean. A few degrees south of the eql the date line has shifted 71ho eastward, avoiding Fiji Tonga island groups which have the same days as , Zealand.

CALENDAR The time taken for the earth to com] one orbit of the sun is called a year. It is measured number of ways-sidereal year, measured with resp€l fixed stars; solar year, time taken by sun to make successive appearances at the point of Aries; and the calendar year which is regulated using leap years so th is equal to that of the solar year (365.2419 mean solar d; To the usual year of 365 days, one day is added in month of February every fourth year, making it a leap year.

This correction, being too large, the leap year is omitted in the century years (1800, 1900, etc.) unless the year is divisible by 400. Thus, the year 2000 was a leap year.

The year is divided into months, originally calculated by the revolution of the moon around the earth. But the lunar month of about 29112 days has now been made slightly longer, whereby the months and seasons occur at the same time every year. Months are further divided into weeks, which are arbitrary divisions made by man, each unit having seven days.

In the ancient past, too, man had devised systems of measuring time. The earliest Roman calendar based on agricultural months is an example. This, however, had drawbacks and was corrected by Julius Ceasar by adding 90 days to 46 Be and declaring each year thereafter to be 365 days, every fourth year being a leap year. But this meant a loss of about three-quarters of a day (18 hours) in a century. It was Pope Gregory XIII who gave the final touch to the calendar, which has now been universally adopted, by decreeing that the last year of a century would be a leap year only if it were divisible by 400. Though near perfect, the Gregorian calendar is not uniformly divisible into quarters of months, neither are the months divisible into equal number of days.
The Babylonians, Sumerians and ancient Egyptians had lunar calendars.