TZ claims that in 1950 there was no DST in Portugal, zone Europe/Lisbon. While it was continuously applied between 1916 and 1965. The sources quoted in file europe are poor, it is only Whitman versus Shanks/Pottenger. I have research online law collection for Portugal at https://dre.pt/ and searched for 'hora de verão'. The results are sparse, but what I find on legal texts does not indicate any interruption of the 1916 law for the year 1950. This Wikipedia page shows a list https://pt.wikipedia.org/wiki/Lista_de_per%C3%ADodos_em_que_vigorou_o_hor%C3... and mentions the Decreto-Lei nº 37048 for 1949-1965. That law says 'first Sunday in April to first Sunday in October. No exception for 1950. Here is a list from the Lisbon astronomical observatory, which says the same thing. http://oal.ul.pt/documentos/2018/01/hl1911a2018.pdf/ I suggest that the rules for Europe/Lisbon should be updated accordingly.