To open the Timer Chest or Zeke's Chest, your device's date/time must match universal time. Therefore your device should be set to automatically sync your date/time.
Steps to check/set this can vary a little depending on your device but it's generally:
- Settings
- General
- Date/Time
- Should be an option to turn on automatic syncing
If there is no automatic syncing option, please sync your device time manually with this site:
https://time.is
Then reboot the game and try to open the Chest again.