When you need to change your time zone OR if FreeBusy wasn't able to automatically detect your time zone. Please go to https://freebusy.io/profile and at the bottom of the page you can manually set your time zone.
If you scroll to the bottom of the profile page you will find the manual timezone change feature:
Which you can change by selecting the time zone that is correct for you:
And then you can save those settings by clicking SAVE.
Finally, you can check what your availability is by opening an incognito window OR a different browser and you can check your availability by opening a link to your availability. This is what your meeting schedulers will see when they open your meeting scheduling link.