Well, I had a look at your request:
My wife needs an app that allows her to select a date from a drop down calendar and then save that date.
But, for me there is not enough information.
What exactly is the goal?
Have a list with already predefined dates or just a calender.
If it's a calender, there are quite some different existing calender types in the forum.
Then, what do you want to do with date? Just save it some where, but what for?
From my experience, I don't like to just answer questions without knowing the whole 'problem' or subject, because in most cases, the answer to the question doesn't solve the real problem.
So, before giving any concrete answer or advice, I would like know a bit more on what you want to do.