Did you know that, if you’ve two or more Macs, then you can turn one or more of them into a Time Machine destination for your other Macs to backup to? *
Essentially, you’re turning the Mac into an home-made Time Capsule for wireless, automated backup. Nice!
Apple outlines the principles in a support doc† but all you need to do is activate Apple’s file sharing (AFP) on the Mac you want to act as the Time Capsule. Open System Preferences, then click Sharing, and check the File Sharing entry in the list.
Of course, this Mac will also need sufficient free hard disk space (2-3x the quantity of data you intend to backup, at least).
On the Mac(s) you want to backup to your new “Time Capsule”, open Finder, click Go > Network, then select the faux-Time Capsule Mac’s entry and login. You’ll need to provide login name and password of that Mac, not the one you’re currently sitting at, and be sure to check the Add To Keychain box too. Then click the Time Machine entry within System Preferences, and the Select Disk button. Choose the Time Capsule Mac’s entry in the list. In future the Macs will connect automatically and invisibly.
And that’s it. Setup is completed, and you can use both Macs as you would normally.
The downside of an approach like this is that the Mac acting as the Time Capsule will need to be switched on for the other Mac(s) to backup to it, but if you’ve a household of Macs in fairly constant use then this isn’t much of an issue.
* For a good intro to Time Machine, see this guide I wrote recently for MacWorld.
† Note how the support doc also mentions that you can attach a USB disk to an Airport Extreme 802.11AC in order to turn it into a Time Capsule; attach an inexpensive 2TB USB drive and this is a cheap(er) way of creating a Time Capsule setup than anything sold by Apple itself.