I use A + for 2 years and I am very happy. I want to know

Hello,

I use A + for 2 years and I am very happy.
I want to know how to:
1) My appointment hours are the afternoon from 16h to 18h. For 2 dates only I'ld like to change to 9hà11h.
2) When I decide to change my appointment's dates, I w'ld like to do this from a certain date; ie from 03.01.2015

Can You tell me how to proceed?

Regards