in another related law, the effecting DST changes are stated explicitly: to be from 6.th. of April 1980 at 2.00 to 28.th. of September 1980 at 2.00. If this is true, this differs slightly from the EU rule in that DST runs to 2.00, not 3.00.
It would have been odd for the 1980 transitions to disagree with both old Danish tradition (1945-1948) and with the then-current EU rules. For now, how about if we assume that the 02:00 of the above source refers to standard time, not wall-clock time, and so the EU rules were in effect?
It would indeed have been strange also to disagree with old Danish tradition, but I decided instead to take the investigation a bit further and contacted a number of danish newspapers by email. Unfortunately I did not get many answers, but one was conclusive, EU rules were indeed followed: ===================== BEGIN Hej J. Nørgaard Vedr. Sommertid som du har sendt en mail angående. I Herning Folkeblad 1980, 26.september står der: Natten mellem lørdag og søndag skal urene stilles ind på vintertid eller rettere normaltid. Det betyder at natten bliver en time længere. Rent praktisk foretages skiftet på den måde, at når klokken er tre natten mellem lørdag og søndag stilles urene en time tilbage. Venlig hilsen Anne-Marie Hansen e-mail: amh@herningfolkeblad.dk ===================== END This is a quote from Herning Folkeblad (News), the 26.th. of September 1980. Quoting from the end of the article the night between Saturday and Sunday the clock is set back from three to two. By the way, I agree with all of Paul Eggerts comments to my suggested corrections to the tz database. I will probably send some more observations on the tz database, but later at a more convenient time (for me). Just a little taster, I think that the Mataveri (Easter Island) time zone change in 1982 was at 13.th. of March 1982 21:00, instead of 14.th. of March at 0:00 as the tz database has it, which in reality means that the actual time was changed from GMT-6 to GMT-7 and then back to GMT-6 four hours later. If the change had taken place at 21:00 the 13.th. of March, then there would be no actual time change, but the time would stay as GMT-6 all of March in 1982 in Easter Island. Regards, Jesper Jesper Nørgaard Welen Email: jnorgard@Prodigy.Net.mx Project Leader (Líder de Proyecto) Software CIMMYT - Centro Internacional de Mejoramiento de Maíz y Trigo Dirección: CIMMYT Int. c/o Jesper Nørgaard Km. 45, Carretera México-Veracruz El Batán Texcoco, Edo. de México CP 56130 MEXICO Tel.: +52 (5) 58-04-20-04 ext. 1374 Fax: +52 (5) 58-04-75-58 Tel. Casa: 53-10-05-95 ó 53-10-97-78 Download the free program World Time Explorer, I made: http://www.cimmyt.org/timezone/index.htm