To modify a reservation, use the command gchres:
gchres [-s start_time] [-e end_time] [-d description] [—debug] [-? | —help] [—man] [—quiet] [-v | —verbose] {[-r] reservation_id}
Example 3. Changing the expiration time of a reservation
$ gchres -e "2004-08-07 14:43:02" 1 Successfully modified 1 Reservation