I overwrote my timetable with the new version by accident

If you have accidentally overwritten your original timetable published on Edupage with the new data just follow these steps:

1. Open the last saved timetable (the newest version) and save it as a new timetable file - so with the new name. Please, see this: How can I edit the timetable saved online

2. Open the previous version of your original timetable - it means the one before the change was made, please see this: How to open previously saved versions of my timetable online

3. Save it with using "Overwrite" option. Please, see this: Options for saving the changes in the timetable

4. Set correct dates of validity for the original timetable: How to change the timetable's name and its dates of validity

5. Publish a new timetable with specified dates of validity How to publish another timetable in case of change during the school year

That is all. Now you have +1 new timetable on your edupage. It is no problem, please see this:
How many timetables can be published during a school year?