You can use DSCC to perform this task. For information, see Directory Service Control Center Interface and the DSCC online help.
Modify the replication schedule.
$ dsconf set-repl-agmt-prop -h host -p port suffix-DN \ host:port repl-schedule:value
For example, if you want to set replication to occur between 2:00 and 4:00 every night, type:
$ dsconf set-repl-agmt-prop -h host2 -p 1389 dc=example,dc=com host1:1389 \ repl-schedule:"0200-0400 0123456"
where 0123456 indicate the days of the week, with 0 representing Sunday, 1 representing Monday, and so on.