I have clients in different time zones

From SimplyBook.me

If you have clients in different time zones, set Show booking page in client timezone and Send notifications in client timezone in Settings -> Main configuration to Yes, so that your clients see booking page in their time zone.
For example: You are in UK, London and your client is in US, Washington. Your opening hours are 9a.m-5p.m GMT, but for your American client the schedule will be 2a.m-10a.m PDT.

If all your clients are in the same time zone, just set NO in both fields.
Client timezone settings path new navigation1.png