How do I enter a birthday without knowing the birth year?

Q: What do you put for a clients birthday when you don't know the birth year?

A: You can pick any year, doesn't matter, point is to create the reminder. Give them the age they wish they were.

A: I enter 1900 just to tag I don't know the year.  Obviously 1900 is so far off, I know it's not correct. I'll eventually go back and add the info as I get it.