Here is a quick shell snippet to change the time machine backup interval on OSX. The time interval is specified in seconds. If you want to change it to 4 hours open terminal and enter:

sudo defaults write /System/Library/LaunchDaemons/com.apple.backupd-auto.plist StartInterval -int 14400

You can restore the default interval with:

sudo defaults write /System/Library/LaunchDaemons/com.apple.backupd-auto.plist StartInterval -int 3600