Please be aware that your booking is for a preferred date and time subject to the availability of the photographer. Photographers have variable schedules, therefore they have asked Online Profile Pros to allow clients to request a specific date and time for each shoot. That way the photography can do their best to clear their schedule for you. In some case the photographer will need to reschedule with you for a slightly different time on the same day. It is rare that a photographer would need to reschedule for a different day but it is a possibility.
In addition, photographers are keenly aware of lighting and getting the best shoot possible. Sometimes photographers will want to adjust the schedule to get the very best lighting. Also, as for on-location shoots weather can be a factor and need to be rescheduled