The time displayed on my fitbit is off. Syncing it on my iMac did nothing towards fixing it. I have been unable to fix it manually by holding in the side button.
If the item came with instructions/users manual, is there not a section that explains how to set the time? If not, and while you're awaiting a reply, please pursue the Fitbit Support site for answers. That's the first place I'd check, if it were me.
Hi! Is this a Fitbit Blaze device, and are you syncing with iOS? This happened to me and it was an issue related to the latest iOS update. You have to download the update on the Fitbit app and it will work again.