I was reviewing some historical zones & rules, and I can across a date for Amsterdam that has me a bit confused. I'm not sure if I'm misinterpreting the records, or whether a record is missing. Lets take Jan 1, 1900 for Amsterdam. The Zone table for Europe/Amsterdam shows: a GMT offset of 0:19:32 (and no rule) until 1835, then a GMT offset of 0:19:32 (and Neth rule) until July 1 1937 - using '%s' for letters So for Jan 1, 1900 I am assuming I should be looking for a rule in the Neth rules records But the first 'Neth' Rule starts 1916. I can easily easily understand that this means that there is no special save amount to apply on Jan 1st 1900, but what letters should I be using for that date given that the zone says the letters should be %s? Since the zone record says '%s' for that date, should there not be a rule record starting in 1835 that gives a save amount of 0, and provides the letters 'AMT'? Thanks