Well that happened quickly. Effective immediately. I'd assume Ontario will follow through with the western portion of the province (at a minimum) shortly. Though given how anti-American the Premier has been, I wouldn't be surprised if he abandons the long-standing plan to wait and switch if/when the USA switches. (Ontario legislation was passed some time ago).
https://www.cbc.ca/news/canada/manitoba/daylight-time-manitoba-9.7347844
