How do you change time zones on your Apple Watch?

Just add the timezone in the timezone part of your iPhone and than use it in one of the watch faces of your apple watch. But your Apple watch changes with your iPhone to.

Hi

The time should update automatically, drawn from your iPhone.

When travelling, if the time on your Apple Watch has not changed automatically to reflect the new time zone shown on your iPhone, then the following steps may help:

Update your iPhone and Apple Watch to the latest software, starting with your iPhone (make a backup first):

• Update the iOS software on your iPhone, iPad, or iPod touch - Apple Support
• Update the software on your Apple Watch - Apple Support

Check your settings:

• On your iPhone, go to: Settings > General > Date & Time > if it is not already enabled, turn on Set Automatically.
• On your iPhone, go to: Settings > Privacy > Location Services:
  • Check that Location Services is enabled.
  • Check that Apple Watch Faces is set to While Using.
  • Tap on System Services (at the bottom) > turn on Setting Time Zone.

If Airplane Mode was previously enabled (such as when travelling):

• Check that Airplane Mode has been turned off on both devices (it must be disabled separately on each):
  • Put Apple Watch in Airplane Mode
  • Travel with iPhone
• Check that the devices have reconnected successfully via Bluetooth (and allow some time for them to sync):
  • If your Apple Watch isn't connected or paired with your iPhone - Apple Support

Restart (normally) both your iPhone and your Apple Watch, turning both devices off together, then restarting your iPhone first:

• Restart your iPhone, iPad, or iPod touch - Apple Support
• How to restart your Apple Watch - Apple Support

If the issue persists, then it may help to unpair and re-pair your Apple Watch:

• The Watch app on your iPhone takes a backup of your watch automatically when unpairing via the app.
• Initially choose to Restore from Backup during set up (most data and settings will be restored, with some exceptions, such as Apple Pay cards, passcode).
• If the issue persists, consider instead unpairing and setting it up as a new watch.
• Unpair your Apple Watch and iPhone - Apple Support
• Set up your Apple Watch - Apple Support