Brooks Harris via tz said:
For example, there is a STDOFF shift at 1971 Oct 31 2:00u from 1:00 to 0:00 (a West shift) in London:
# Zone NAME STDOFF RULES FORMAT [UNTIL] Zone Europe/London -0:01:15 - LMT 1847 Dec 1 0:00s 0:00 GB-Eire %s 1968 Oct 27 1:00 - BST 1971 Oct 31 2:00u 0:00 GB-Eire %s 1996 0:00 EU GMT/BST
Zic and TzIf reflect this change as a shift in gmtoff, not stdoff:
57722399 1971-10-31 02:59:59 isdst 0 gmtoff 3600 stdoff 0 BST 57722400 1971-10-31 02:00:00 isdst 0 gmtoff 0 stdoff 0 GMT
That's what I mean by "adjusted" for Posix sake. It gives the proper UTC offset, yes, but not for the right reason. The underlying reason was an STDOFF shift, presumably stated in the law behind it.
The reason in this case was that the British Standard Time Act 1968 c.45 contained a sunset (sorry) clause: 4(2) Sections 1 to 3 of the Act shall expire at two o'clock, Greenwich Mean Time, in the morning of 31st October 1971 unless made permanent under subsection (3) below; An attempt to make it permanent was defeated in the House of Commons on 1970-12-02 by 81 votes to 366. See Hansard HC Deb 02 December 1970 vol 807 cc1331-422. Therefore 4(2) came into effect and on that date the legal time changed from that specified in the British Standard Time Act (GMT+1) to that specified in the [1880 c.9 (43 & 44 Vict.).] Statutes (Definition of Time) Act 1880 (GMT) as modified by the Summer Time Acts 1922 to 1947. -- Clive D.W. Feather | If you lie to the compiler, Email: clive@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646