How to schedule PostgreSQL replication?

I was reading postgresql replications solution but, even I just starting understaning how it works, another doubt has arrisen. I'll be using postgres internal replication solution but as far as I understand, every event will be replicated just as it is achieved; for example, if I insert some data into the master, automatically it will be replicated to the slave...Am I right? Well, is that so, I was searching for way of scheduling this replications as a passive backup but the thing is, I need for example, every monday on the night the database gets replicated with all the data it had inserted in it that day to a slave database in Amazon EC2 virtual servers. I was thinking on using cron as a first approach but reading postgres documentation I got aware that practically only configuring the necessary files, postgres do it for you... So, how could I schedule replication in just desired moments? PD.-The schedule may vary so it needs to be completely generic, also...I'm using Ubuntu 12.04 and PostgreSQL 9.1 as in the master as in the slave. Thanks