| Ottawa Collingwood | Eastern Australia Time | -15:00 |
| Ottawa Carleton Place | Eastern Time | 00:00 |
| Ottawa Cologna Veneta | Central European Time | -06:00 |
| Ottawa Carle Place | Eastern Time | 00:00 |
| Ottawa Cologne | Central European Time | -06:00 |
| Ottawa Carlingford | Ireland Time | -05:00 |
| Ottawa Collingswood | Eastern Time | 00:00 |
| Ottawa Carlin | Pacific Time | 03:00 |
| Ottawa College Place | Pacific Time | 03:00 |
| Ottawa Carlton | Eastern Australia Time | -15:00 |
| Ottawa Collegeville | Eastern Time | 00:00 |
| Ottawa Carlton North | Eastern Australia Time | -15:00 |
| Ottawa Cold Spring | Eastern Time | 00:00 |
| Ottawa Carmel-by-the-Sea | Pacific Time | 03:00 |
| Ottawa Coldwater | Eastern Time | 00:00 |
| Ottawa Carnac | Central European Time | -06:00 |
| Ottawa Colfax | Pacific Time | 03:00 |
| Ottawa Carnforth | United Kingdom Time | -05:00 |
| Ottawa Colborne | Eastern Time | 00:00 |
| Ottawa Chippewa Falls | Central Time | 01:00 |
| Ottawa Chagford | United Kingdom Time | -05:00 |
| Ottawa Chipping Campden | United Kingdom Time | -05:00 |
| Ottawa Chablis | Central European Time | -06:00 |
| Ottawa Chipping Norton | Eastern Australia Time | -15:00 |
| Ottawa Chadstone | Eastern Australia Time | -15:00 |
| Ottawa Chinon | Central European Time | -06:00 |
| Ottawa Chae Ramae | Indochina Time | -11:00 |
| Ottawa Caroline Springs | Eastern Australia Time | -15:00 |
| Ottawa Chakpachuria | India Standard Time | -09:30 |
| Ottawa Carole Park | Eastern Australia Time | -14:00 |
| Ottawa Chamonix | Central European Time | -06:00 |
| Ottawa Carolina Beach | Eastern Time | 00:00 |
| Ottawa Chamblee | Eastern Time | 00:00 |
| Ottawa Chilmark | Eastern Time | 00:00 |
| Ottawa Chalong | Indochina Time | -11:00 |
| Ottawa Chiloquin | Pacific Time | 03:00 |
| Ottawa Chimney Rock | Eastern Time | 00:00 |
| Ottawa Chimgan | Uzbekistan Time | -09:00 |