You can make logbook entries as long back as you like. However, your resume shows the totals with in the last 2 years, 5 years and 10 years. Although it does present the total amount of sailing days as well. To say this: Charter companies really only care about the last 10 years of sailing when determining your eligibility to charter one of their boats. Anything after ten years is not taken very much into account. Some but not much.
But go ahead and enter what you like.
To make old way back entries, you'll need to tap the grey part of the calendar below a few times to make it so that you can jump back years. First time you tap the calendar icon you'll see the current month and current year. Tap that and it will allow to jump to months, tap it again and it allows to jump years.