Can't help you with JS code, but I can with APEX. There's a freebie Stop Watch class that's part of Apex Utilities which you can get from either the App Exchange or get the source code here (https://code.google.com/archive/p/apex-lang/). If you downloaded the source code, I'd think you could readily incorporate portions of it into a custom controller for your wizard.
Can't help you with JS code, but I can with APEX. There's a freebie Stop Watch class that's part of Apex Utilities which you can get from either the App Exchange or get the source code here (https://code.google.com/archive/p/apex-lang/). If you downloaded the source code, I'd think you could readily incorporate portions of it into a custom controller for your wizard.