Important - Signing up only applies to the meeting organizer. People you schedule with never have to sign up.
 

ScheduleOnce does not ask the user to register, and as a result, it does not have its own user name and password. Instead, ScheduleOnce allows you to login with a Google or Facebook ID. This login mechanism is completely secure and ScheduleOnce does not know your login details. The only thing that ScheduleOnce knows is your name and email address.
 

What if I don't have a Google or Facebook account? 

Just open one. It takes less than a minute and you can open it on any email address:
 

To open a Google Account on any email address click here: https://www.google.com/accounts/NewAccount

To open a Facebook account on any email address click here: http://www.facebook.com/r.php
 

I already have a Google or Facebook ID but I want to use another email address

This is easy. Sign up with your existing Google or Facebook ID, complete the initial wizard and then go to the Account page. In your Account page you can see the email address that belongs to the ID with which you signed up. If you want to receive all ScheduleOnce communication in another email address simply change it and save. Note that this does not change your login email. You will still need to login with the email address that belongs to your Google or Facebook account, but all email communication from ScheduleOnce will be delivered to the new email address you provided.