| Istra Corte Madera | Pacific Time | 10:00 |
| Istra Ossipee | Eastern Time | 07:00 |
| Istra Cimadolmo | Central European Time | 01:00 |
| Istra Ostia | Central European Time | 01:00 |
| Istra Cifuentes | Central European Time | 01:00 |
| Istra Ostrava | Central European Time | 01:00 |
| Istra Cidade Ocidental | Brasilia Time | 06:00 |
| Istra Ostrava | Central European Time | 01:00 |
| Istra Cottonwood | Mountain Time | 10:00 |
| Istra Ostermundigen | Central European Time | 01:00 |
| Istra Cottage Grove | Pacific Time | 10:00 |
| Istra Osterwasser | Central European Time | 01:00 |
| Istra Cotgrave | United Kingdom Time | 02:00 |
| Istra Pano Panagia | Eastern European Time | 00:00 |
| Istra Costa Teguise | Western European Time | 02:00 |
| Istra Pannipitiya | India Standard Time | -02:30 |
| Istra Cotati | Pacific Time | 10:00 |
| Istra Panindícuaro | Central Time | 08:00 |
| Istra Costa da Caparica | Western European Time | 02:00 |
| Istra Costa d'en Blanes | Central European Time | 01:00 |
| Istra Cosmopolis | Pacific Time | 10:00 |
| Istra Covington | Central Time | 08:00 |
| Istra Cowaramup | Western Australia Time | -05:00 |
| Istra Court-St.-Etienne | Central European Time | 01:00 |
| Istra Courthézon | Central European Time | 01:00 |
| Istra Cova da Piedade | Western European Time | 02:00 |
| Istra Coulter | United Kingdom Time | 02:00 |
| Istra Courmayeur | Central European Time | 01:00 |
| Istra Cozumel | Eastern Time | 08:00 |
| Istra Cramlington | United Kingdom Time | 02:00 |
| Istra Fort Gratiot Township | Eastern Time | 07:00 |
| Istra Fort Irwin | Pacific Time | 10:00 |
| Istra Fort Langley | Pacific Time | 10:00 |
| Istra Fort McMurray | Mountain Time | 09:00 |
| Istra Fort Mill | Eastern Time | 07:00 |
| Istra Fort Mohave | Mountain Time | 10:00 |
| Istra Ellaville | Eastern Time | 07:00 |
| Istra Ellenville | Eastern Time | 07:00 |
| Istra Fort Erie | Eastern Time | 07:00 |
| Istra Ellis | Central Time | 08:00 |
| Istra Ellisville | Central Time | 08:00 |
| Istra Elbigenalp | Central European Time | 01:00 |
| Istra Elda | Central European Time | 01:00 |
| Istra Elkhart Lake | Central Time | 08:00 |
| Istra Elkhorn | Central Time | 08:00 |
| Istra Elkins | Eastern Time | 07:00 |
| Istra Elexalde | Central European Time | 01:00 |
| Istra Elen | Central European Time | 01:00 |
| Istra Elizabeth | Central Australia Time | -06:30 |
| Istra Elizabeth Bay | Eastern Australia Time | -07:00 |