When you are manually entering birthdates and anniversary dates in your online address book, the calendar picker only displays the last 10 years (e.g. 2008 - 2018). To select a year more than 10 years in the past simply select the oldest date, and the calendar tool refreshes and lets you pick the prior 10 years. By jumping back 10 years at a time, you can assign any date in the past.
Alternately, if your browser or device supports it, you can just select any year and date with the calendar tool, and then click in the date field to over-write the date by typing into the date box.