Fitbit app Open → tap Profile ➡ Advanced Settings ➡ Time Zone. Disable the option of Set Automatically, set the right zone and sync your device. In the event of troubles, restart your Fitbit and re‑pair Bluetooth. This tends to address the problems on time differences in a short period of time!
To change the time on your Fitbit, sync it with the Fitbit app (which automatically updates the time) or manually adjust it in the Settings > Clock Face > Time Zone on your device.
To change the time on your Fitbit, open the Fitbit app, go to Settings > App Settings > Time Zone, turn off auto, set your time zone manually, then sync your device.