If you do not keep your computer turned on during nights, it is likely that all the maintenance scripts have not run properly. To manually run those cleanup scripts, open Terminal and type the following:

$ sudo periodic daily weekly monthly

Type your Admin password when prompted. The scripts will run in sequence but no feedbacks will be given. When each of those scripts run, they will write to their logs and you can check those log files to know when they were last run.

$ ls -al /var/log/*.out
-rw-r--r-- 1 root wheel 574968 Jul 31 08:24 /var/log/daily.out
-rw-r--r-- 1 root wheel 2343 Jul 31 08:25 /var/log/monthly.out
-rw-r--r-- 1 root wheel 5077 Jul 31 08:24 /var/log/weekly.out

In this example, all three scripts last ran on 31st July.