To dial Canada from outside the U.S/Caribbean (Country Code 1), dial the IDD prefix + 1 + Area Code + Local Number

To dial from the U.S./Caribbean, dial 1 + Area Code + Local Number Toronto has required 10-digit dialing since 8 January 2001.  

Toronto got a new area code (647) on 5 March 2001, and local 10-digit dialing began. Click here for more. Communities in the 905 area code have required 10-digit dialing since 7 April 2001.

Since 9 June 2001, area code 905 has shared an "overlay" with a new area code, 289.  Click here for more. On 3 November 2001, the new area code 778 overlay was introduced in the 604 region of British Columbia. 

Beginning 11 August 2001, permissive dialing with 10 digits began; 10-digit dialing became mandatory on 3 November 2001. 

For a discussion of upcoming area code changes in the U.S. and Canada, refer to http://areacode-info.com