Booking up to 30 days

Dear all,

Nice plugin suits my needs.
I setup all the events to be bookable from 30 days before, up to 6PM the day before the event starts.
The second part is working fine.
The first part goes up to 29 days before the event start.
For example today, it is possible to book an event until September 11th, not September 12th.
I am in Japan, maybe there is a configuration file somewhere (over the rainbow) that I need to modify.
WordPress is setup with Japanese time.
Thank you,
George