Calendar is the mode of adjusting the natural divisions of time with respect to each others for the purpose of civil life. An almanac is table of months, days and seasons, or of special facts etc.
Counting of time by days, months and seasons began very early in men’s history.
The Greeks dated everything from the beginning of the Olympic register. It was a traditional list of victors in the Olympic Games. It started in the year 776 B.C.
The Romans counted time from the founding of their city in 753 B.C.
The Hebrew Calendar dated back to 3760 years and three months before the beginning of the Christian era.
Christian nations throughout the world date events from the birth of Christ.
Buddhist calendar is reckoned from the death of Buddha in 553 B.C. (actual date being 487 B.C). The Buddhist year starts from Vaisakhi Purnima.
Hindu calendar employs luni-solar cycles made by the combination of solar years and lunar years so treated as to keep the beginning of the lunar year near to that of the solar year.
The solar year is divided in to twelve months according to the successive entrances of the sun into the sidereal signs of the zodiac. The lunar year consist of the twelve lunar months. It is of two kinds according as it begins with certain day in Chaitra or with the corresponding day in Kartika.
Islamic calendar dates from Hijra of the Prophet Muhammad (S.A.W) from Mecca to Medina in 622 A.D. The Hijri era is purely lunar. It consists of twelve months being of 30 or 29 days. The mean length of Hijra year is 354 days, 8 hours and 48 minutes and the period of mean lunation is 29 days, 29 hours and 44 minutes.
Julian calendar was started by Julius Caesar in 46 B.C. The object of this calendar was to adjust the extreme errors which had crept in to the civil year. The beginning of the year was changed from March 1 to January 1.
Jewish calendar is a luno-solar calendar. The year is solar while months are lunar. In a cycle of 19 years the 1,2,4,,5,7,9,10,12,13,15,16,18 years have twelve months. The remaining years have 13 months of 29 and 30 days each. The length of the ordinary years may be 353,354 or 355 days. The mean length of the year over a 19 years cycle is just over 365 days.
The years are reckoned from 3760 to B.C. Thus the year 1963 A.D is A.M (Anna Mundi) 5723. The days begin at sunset.
Gregorian Modern Calendar was introduced in 1583 A.D. It was based on the Julian calendar. The Julian calendar was modified by Pope Gregory 8. The idea was to adjust the calendar to the tropical year, because Julian calendar had left 11 minutes and 14 seconds resulting in an error of 10 days since its adoption.
Each year is of 35 days with every fourth year as a “Leap year” of 366 days. The Julian calendar reckoned the length of a year as 35 ¼ days whereas it is actually of 35.2422 days.
The international fixed calendar league has placed a calendar of 13 months each of 28 days and a New Year day which comes between December 28, the last day of a year and January 1, the beginning of the next.
The thirteenth month Sol comes between June and July. In a leap year a day is inserted between June and Sol. The main advantage of this scheme is that the same date always falls on the same day of the week.
Indian national calendar was adopted for official purposes along with the Gregorian calendar from zero hour on March 22, 1957. This calendar is based on the “Saka” era which began with the vernal equinox of 78 A.D. corresponding to 1878-79 of the Saka era.
The years consist of 365 days except that a leap year contains an extra day. The New Year seeks to prevent mistake occurring in fixing the length of the year or the month. Seven months are of 30 days each and five months are of 31 days each. In a leap year 6 months are of 30 days each and the rest are of 31 days each.
The proposed world calendar requires that the year should be divided into four quarters, each containing 13 weeks of 91 days or 3 months, commencing on Sunday and ending on Saturday. The months of January, April, July and October will contain 31 days each the remaining 8 months 30 days each. 365 days (extra Saturday) will be named as world day and may be considered as world holiday.