Time lag between booking on google calendar and booking on appointments+

Hi,

Sorry for all the posts and questions. I suppose that it's better that i do one different post for each question. Tell me if, in the futur, you prefer me to put everything in a single post.

So, i've got a little problem:
The sync gAgenda and appointments+ works fine but there is a time lag:
When a booking is made at 9.30 on appointments+ (a client through the website), it appears à 10.30 on the provider's gAgenda. It's the same if the client wants to copy the booking on his gAdenda: there is one hour of time lag:
I let you know that i do this from France and the officiel time is GMT+1. Is there any link with my problem?

Thank you very much
Mathieu