Notes and examples
A Julian day algorithm is used in all calculations of DATE. The transition
date is 18.2.1753, when Finland (as part of Sweden that time) changed to
the Gregorian calendar. The algorithm is valid from 4713 B.C. to 9999 A.D.
DATE supports years from 200 A.D. The years 0-99 mean the current century. [*]
Source: Calendrical Calculations, by Nachum Dershowitz and Edward M. Reingold.
In Software-Practice and Experience, 20, number 9 (September 1990), pp899-928.
[*] When working with Survo data sets, the specification CENTURY may be used
to change this behaviour. For example: CENTURY=1900 (default: CENTURY=2000).
In addition, specification SHIFT is available for working with dates that
range over the turn of the century and are represented (in the data set)
with two digits only. For example: SHIFT=75 (with the default CENTURY=2000)
means that years 75-99 are handled as 1975-1999, whereas years 0-74 will be
handled as 2000-2074. By default, SHIFT=0. CENTURY always overrides SHIFT.
Examples: (given in 1997)
DATE 18.2.1753 / Thursday March 01 1753 21:41:50 Week=09 Day=049
The gap of 10 days corrected the accumulated error in the Julian calendar:
DATE 1.3.1753 / Thursday March 01 1753 21:41:51 Week=09 Day=049
DATE 1.3.1753+85416 / Saturday January 10 1987 21:41:53 Week=02 Day=010
DATE 31.12.99+1 / Saturday January 01 2000 21:41:56 Week=52 Day=001
DATE 29.2.2000-60 / Friday December 31 1999 21:41:56 Week=52 Day=365
But,
DATE 31.12.99+1 / Friday January 01 2100 00:26:10 Week=53 Day=001
(given in 2000)!
Hence, it is always recommendable to use four-digit numbers for years.
D = More information on DATE operation
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