For chartering purposes, the charter companies are really more interested in the past ten years experience. There is a diminishing return on older experience.
So you really want to enter mostly any experience with in the past ten years. If there is not much and you are picking sailing back up again after a long break - well then perhaps go back 15 years.
To start however, start with the most recent experience then move backwards in time. You should be aiming to document at least 50 days of sailing experience.
Of course we don't and no one else either expects you to get the dates correct. So do it like this - if last year you sailed 5 times about, then think about (very about) how many of those were in the spring - the summer - the fall. Then enter general approx dates the match somewhat possible the season.
In general - don't stress on this - just do a decent job as best you can.
Then keep going back in time like that until you get the required amount of days.
Make sure you create/add your vessels then enter the time on those vessels that you have set up or you may use the Common Vessels that we have already set up for you. See this article on that.