Nokia Lumia 925 - After updating to Lumia Cyan, my calendar app shows time in 12 hour format. What can I do?

1. Go to Settings > region and see if Regional Format is set correctly.

2. If you have changed your phone's display language to English United States; set it to English United Kingdom. Go to Settings > language:

  • If English (United Kingdom) appears on the language settings screen, long tap on it and select move up.
  • Or add a new language: Tap + add languages, select English (United Kingdom) and tap Done.

3. The phone restart will be required.