Even if yum didn't provide any cron jobs, you can simply create one yourself: run
find out the time format, i.e. how you specify the run time, then as root run
and fill in a command to run yum at the specified time with needed arguments.
However if I were you I didn't do it. It doesn't take you that much time to run it when you're at the machine, but if you run it at 1pm and something goes wrong (as it well can go), you're in trouble. Also as the administrator, no matter how "just my pc" it is, you shouldn't let anybody -- even a yourself-defined cronjob, or especially that -- install any software without reviewing it/them. It's just foolish, if you ask me
the easiest thing to keep a working, fine-running system working well is to not install updates to it without making sure they work. You think it's silly, that you can just go ahead and install the updates since they are "tested", but if you spend some time looking around at how much trouble people get by updating software without checking what's going on, you'll notice it's wiser to not automate any updates. It's a security threat also, since if at 1am you do an update of software chich creates a big security hole, and at 2am somebody gets to know it and wants to wrech-havoc your machine, you wouldn't even have woke up before it's all gone. Sounds very unprobable, but is possible.
Maybe the most famous, especially among newbies, are situations where somebody "did an update, don't remember what was updated" and then your screen is just blank, OS won't boot, bootloader blinks only two letters and kernel panics. And why? Just because you didn't check out what was updated -- this way you don't even know where to start looking