I noticed changes in the DST->STD transition dates to the follwing week mentioned in an Alexandria, Ontario weekly newspaper article linked from a page on an unrelated issue, and checking that against zdump found that 1949 & 1950 appear to have transitioned in November, rather than September as in other years from 1946-1956, which from comments in northamerica, appear to derive from Shanks & Pottenger. So I also downloaded the same paper's issue from the same week of September in the other questionable year, and found another article announcing the change that weekend. As well as time being the lede in top of front page articles about municipal business, there are also municipal notices of time changes in later pages, as well as Canadian National railway ads announcing updated time tables being available from that weekend, and an article listing updated CNR train times from Montreal, and a mention of a follow up when Montreal time changes the weekend following Ontario cities. The attached files show relevant edited pdftotext extracts from the PDFs. Note that the municipality changed its time a day leter than elsewhere in Ontario, midnight Sunday/Monday rather than Saturday/Sunday, so that people will not miss Sunday church services, but Monday work does not matter! [Canada traditionally calls the prairie provinces the "Bible Belt" and there are visible signs of that, including dry municipalities where alcohol was not available, but that did not stop many bars and shops in nearby towns opening Sundays, if there was enough business to be worth it, whereas many eastern provinces had legal restrictions on stores and bars opening on Sundays until recently.]