But I already use Calendar/Contacts/Facebook. Why Dearly?
Three places already hold the date. None of them help you plan around it.
You don't have to start over. Dearly can import dates from Contacts or your calendar in minutes. Facebook import is not available.
Calendar
Does well
Calendars are dependable. Put the date in once, and it's there every year without fail.
Falls short
There's no sense that some people deserve more lead time than others. A birthday sits in the same box as a dentist appointment, with the same alert and the same weight.
Contacts
Does well
Contacts keep the date right where it belongs: next to the person, not buried in a calendar view.
Falls short
Nothing about a contact card looks forward. The date just sits there until you happen to open it, which is rarely before the day itself.
Does well
Facebook still surfaces birthdays in a feed, and it's the only one of the three with any real list view of what's coming up.
Falls short
The reminder happens in public, and often the wish does too. Fewer people open it regularly now, so the reminder is easy to miss.
None of that makes them bad tools. It just means important dates need a place built around the people they belong to.