You can cancel your first travel day or 1-month Pass validity period any time before the start of that period (00:00 CET). If you’ve already scheduled a travel day, go to your Pass in My Pass and tap 'Cancel travel day' and then ‘deactivate Pass’. If you haven’t scheduled your first travel day yet, go to your Pass in My Pass and tap ‘deactivate Pass’. You can then choose a new Pass validity period day by finishing the activation in My Pass again, after which you can plan your new travel days.
You can also choose an earlier date when using a new travel day, which will then become your first travel day, provided you still have travel days available on your Pass. Your Pass validity period will change to match this new start date.
Please note that some European countries do not observe Central European Time (CET). This means there can be a difference in the start and end time of a travel day when compared to your local time while travelling.