<P> Area codes 905, 289, and 365 are overlay area codes in the North American Numbering Plan (NANP) in Southern Ontario, Canada, particularly covering the Niagara Peninsula, the city of Hamilton, Halton Region, Peel Region, York Region, and Durham Region . Area code 905 was assigned on October 4, 1993, as a split from area code 416 . After 289 was overlaid on June 9, 2001, all local calls required ten - digit dialling . On April 13, 2010, the Canadian Radio - television and Telecommunications Commission (CRTC) introduced the overlay area code 365, which became operational on March 25, 2013 . The three area codes are expected to become exhausted by March 2025 . </P> <P> The plan area surrounds the overlay area codes 416 / 647 / 437, which cover the city of Toronto, leading residents to popularly coin suburban Toronto as "the 905". It is bound by area code 519 / 226 in the west, 705 / 249 in the north, 613 / 343 in the east, and New York State area code 716 on the eastern prong of the Niagara Peninsula . The incumbent local exchange carrier for these area codes is Bell Canada . </P>

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