Suppose you have two dates and you want to compares the years rather the exact date. Make sure you know the format of the dates. The use the following code:

to_char(to_date(somedate, 'yyyymmdd'), 'YYYY') = to_char(to_date(somedate, 'yyyymmdd'), 'YYYY')

Change yyyymmdd to your date format.

This example have been tested on Oracle 8i, 9i, 10g, and 11g.