Sorry about the delay getting back with this information.
I'm working on a rewrite of `europe' with a large set of historical data. My current draft (see below) claims that Iceland changed its timezone in 1968. I've taken this claim from Thomas G. Shanks, The international atlas (3rd edition), San Diego: ACS Publications, Inc. (1991). If you have some better data, please let me know.
In a way, there was a timezone change in 1968, where the summertime change was applied during the spring, and became the all-year-round time, and there have been no changes since then, not for DST or any other reason. When looking back to previous years when there was DST, icelanders tend to refer to the concept of "winter time", as the summer time had the same offset as the present all-year-round time. This is why I was led to believe that no timezone change had taken place in 1968.
It would be nice to know what time zone abbreviations were used before 1968, since Shanks doesn't say. In the following table I've made up the names `IST', `IDT', `RMT', and `LMT' for Iceland Standard Time, Iceland Daylight Time, Reykjavik Mean Time, and Local Mean Time respectively.
I have no details of any abbreviations, sorry.
# From Shanks (1991): # Rule NAME FROM TO TYPE IN ON AT SAVE LETTER/S Rule Iceland 1908 only - Jan 1 0:00 0 S Rule Iceland 1917 1918 - Feb 20 2:00 1:00 D Rule Iceland 1917 only - Oct 25 2:00 0 S Rule Iceland 1918 1919 - Nov 15 2:00 0 S Rule Iceland 1919 only - Feb 19 2:00 1:00 D Rule Iceland 1921 only - Mar 19 2:00 1:00 D Rule Iceland 1921 only - Jun 22 2:00 0 S Rule Iceland 1941 1942 - Mar Sat>=1 2:00 1:00 D Rule Iceland 1941 1942 - Jul 2 2:00 0 S Rule Iceland 1943 1946 - Mar Sun>=1 2:00 1:00 D Rule Iceland 1943 1948 - Oct Sun>=22 2:00 0 S Rule Iceland 1947 1962 - Apr Sun>=1 2:00 1:00 D Rule Iceland 1949 only - Oct 30 2:00 0 S Rule Iceland 1950 only - Oct 22 2:00 0 S # From Paul Eggert <eggert@twinsun.com> (November 10, 1993): # Shanks's ``1953 Oct 26'' is probably a typo for Oct 25. # Likewise, correct Shanks's ``1961 Oct 22'' to Oct 29. Rule Iceland 1951 1967 - Oct Sun>=23 1:00s 0 S Rule Iceland 1963 1968 - Apr Sun>=1 1:00s 1:00 D # Zone NAME GMTOFF RULES/SAVE FORMAT [UNTIL] Zone Atlantic/Iceland/Reykjavik -1:27:24 - LMT 1837 Jan 1 -1:28 - RMT 1908 Jan 1 -1:00 Iceland I%sT 1968 Oct 27 1:00s 0:00 - GMT # This link is for backward compatibility with the old naming convention. Link Atlantic/Iceland/Reykjavik Iceland
I don't feel up to messing with this table and submitting a corrected version. Here I copy a list of periods when summertime was active, and explanatory text. This material is paraphrased from the 1988 edition of the University of Iceland Almanak.
From January 1st, 1908 the whole of Iceland was standardised at 1 hour behind GMT. Previously, local mean solar time was used in different parts of Iceland, the almanak had been based on Reykjavik mean solar time which was 1 hour and 28 minutes behind GMT.
Summertime when it was applied was always by putting the clock an hour forward during the summer months, which made the clock time equal to GMT. The following list shows when this summertime was in force. The time of the clock change is specified in GMT. year from to ---- ---- -- 1908-1916 no summertime 1917 20.Feb. 0:00 21.Oct. 1:00 1918 20.Feb. 0:00 16.Nov. 1:00 1919-1938 no summertime 1939 30.Apr. 0:00 29.Nov. 2:00 1940 25.Feb. 3:00 3.Nov. 2:00 1941 2.Mar. 2:00 2.Nov. 2:00 1942 8.Mar. 2:00 25.Oct. 2:00 1943-1946 rule (first Sunday in March until first Sunday in winter) 1943 7.Mar. 2:00 24.Oct. 2:00 1944 5.Mar. 2:00 22.Oct. 2:00 1945 4.Mar. 2:00 28.Oct. 2:00 1946 3.Mar. 2:00 27.Oct. 2:00 1947-1967 rule (first Sunday in April until first Sunday in winter) 1947 6.Apr. 2:00 26.Oct. 2:00 1948 4.Apr. 2:00 24.Oct. 2:00 1949 3.Apr. 2:00 ******* 30.Oct. 2:00 (delayed by 1 week) 1950 2.Apr. 2:00 22.Oct. 2:00 1951 1.Apr. 2:00 28.Oct. 2:00 1952 6.Apr. 2:00 26.Oct. 2:00 1953 5.Apr. 2:00 25.Oct. 2:00 1954 4.Apr. 2:00 24.Oct. 2:00 1955 3.Apr. 2:00 23.Oct. 2:00 1956 1.Apr. 2:00 28.Oct. 2:00 1957 7.Apr. 2:00 27.Oct. 2:00 1958 6.Apr. 2:00 26.Oct. 2:00 1959 5.Apr. 2:00 25.Oct. 2:00 1960 3.Apr. 2:00 23.Oct. 2:00 1961 2.Apr. 2:00 22.Oct. 2:00 1962 1.Apr. 2:00 28.Oct. 2:00 1963 7.Apr. 2:00 27.Oct. 2:00 1964 5.Apr. 2:00 25.Oct. 2:00 1965 4.Apr. 2:00 24.Oct. 2:00 1966 3.Apr. 2:00 23.Oct. 2:00 1967 2.Apr. 2:00 29.Oct. 2:00 1968 7.Apr. 2:00 (actually GMT after this) "first day of winter" referred to above, means the first day of the 26 weeks of winter, according to the old icelandic calendar that dates back to the time the norsemen first settled Iceland. The first day of winter is always Saturday, but is not dependent on the Julian or Gregorian calendars. This is the reason for the discrepancy with October 1961. I can find out more exactly how to determine when it falls, if necessary. It is a pity I don't have that information handy, otherwise I could include it here. There are more serious discrepancies before 1941 which are not obviously explainable. What to do... (?) -- Adam David <adam@veda.is>