I have a Dx and will probably trade it in, when the DIncs are more available. I love my X but the size of the thing is what makes me want to switch. I have a couple more weeks to decide but I think I've made up my mind.
Go to the Settings page, select the Calendars tab and click on "Browse Interesting calendars", then go to the More tab and subscribe to the calendar "Contacts' birthdays and events".