A quick way is to look at the logbook in the Agenda.
You can look at the agenda (see Agenda Views in Org Mode docs). Move the agenda to the time period you want - day, week, month, year. Put it in logbook mode (via the 'l' key, described in section 10.5 Commands in the agenda buffer). This will show for that time period which tasks you worked on and when.
You can also use a clock table (see section 8.4.2 The clock table) to get a detailed report where you can set all the details of what you are interested in.
(Note: the section heading numbers I refer to are in Org-mode version 8.2.5h - your version may differ, but those sections will still be there)
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…