Thanks for the research and spreadsheet. It is very useful. Being Canadian, I am intruiged by Ottawa, which is the capital of Canada, the second largest city in Ontario, and the fourth largest in Canada. It seems that since 1970, Ottawa and Toronto and Montreal have followed the same timezone/saylight saving rules, but prior to that, Ottawa and environs was likely more in sync with Montreal's daylight saving rules than Toronto's rules for proximity and commercial reasons. As well, Montreal, not Toronto, was the largest city in Canada until about 1975. So, as far as I understand the rules, Ottawa does not require a link in tz at this time - but if a link for capitals is ever added in tz - the preferred link for Ottawa should probably be Montreal, not Toronto.