Even if you never give a photo a title, description, or keywords, you can always search by date, since your camera records the date and time when you take a photo.
And remember, you can use iPhoto to adjust the dates of your photos to make date searches as accurate as possible (page 23).
When you display the Calendar panel, it shows the current year.
Tip: If you point to a month or date without clicking, iPhoto tells you how many photos you took during that month or on that date, as shown here. ...