(bug) wrong date

Hello,

We are using Webba booking for almost two years. It works really great, but after today something changed. It seems that there is a bug inside.

When we/our customer select an date to make an appointment, timeslots will be showed a day before.

Example:
1) Customer select date 18th of November
2) Timeslots showed are 18th of November but with the date 17th of November
3) Customer received confirmation mail with the info booked on 17th of November
4) Booking in Google Calendar is on 18th November
5) In shedules: 17th of November is blocked. Its not possible to book. So the timeslots of 18th November are shown.

Does anyone knows how we can solve this?

Br
Ferdinand