2.1.100 [ECMA-262-1999] Section 15.9.1.9, Daylight Saving Time Adjustment

V0152:

If the host environment provides functionality for determining daylight saving time, the implementation of ECMAScript is free to map the year in question to an equivalent year (same leap-year-ness and same starting week day for the year) for which the host environment provides daylight saving time information. The only restriction is that all equivalent years should produce the same result.

JScript 5.x does equivalent year mapping to determine daylight savings time adjustments. The equivalent year that is used is determined according to the following table:

Week day of Jan. 1:	0	1	2	3	4	5	6
Non-leap years < 2007	1995	1979	1991	1975	1987	1971	1983
Leap years < 2007	1884	1996	1980	1992	1976	1988	1972
Non-leap years ≥ 2007	2023	2035	2019	2031	2015	2027	2011
Leap years ≥ 2007	2012	2024	2036	2020	2032	2016	2028