The largest log is the System Log. Here the file
/var/log/messages will be interpreted.
The system log is divided into several sections and each section can be selected from the drop down menu Section. The date for viewing is selected under Month and Day.
After a Section is chosen the content of the selected section (log) will be displayed after a click on Update. Below is an example from the section NTP:
Want to view the log for the entire month? Change the Day: to All at the top of the Day list.