Hello Bejilie21
The rule is the following:
The first day of validity is considered a whole day for the calculation of the validity period. The validity period starts at 00.00am on the first day of validity and expires at 05.00am on the day after the last day of validity.
The passes will be valid until September, 1st at 05.00am.
I recommend to buy such passes with an account and not as guest. You can show the tickets (QR codes) as PDF file or in the SBB Mobile app. You can send or share the PDF file to other devices and/or print it. It should also be possible to install the app on other devices and make a login with the same account.
Do you have children under 16 in your family? They can travel free of charge with the Swiss Family Card, but don’t forget to indicate their names and dates of birth when you order the passes. You must confirm that you are the parents.
Kind regards
Danhiel