You need to make your best effort to state your international travel history on your N-400 Naturalization Application Form. You can state that the dates and length of stays are estimates on the form, but it is important to at least list the various countries that you visited. If you would like assistance with preparing and filing your Naturalization Application, please contact us at 206-624-8410 or email at firstname.lastname@example.org. Good luck with your application!
I've run into this situation many times. There is a government database you can use to retrieve information regarding all of your trips abroad (not Canada). I would suggest requesting all of your information from this database prior to filing the N-400.
Both the previous answers are good. In my experience it is most difficult for people to remember the exact dates of their trips. Obviously it is best to provide the most complete and accurate data that you can, but I think in most cases if you accurately list the countries you visited, the approximate dates, and the lengths of time you were outside the U.S. this is sufficient. I believe the principle purpose of this section is to determine if you meet the residency requirements for citizenship and to be sure that the applicant has not abandoned his or her residency.