Default date widget so it is 18 years ago

1. What is the problem? Be very detailed.
I have a few date questions on a survey where I would like the default appearance to have the year at least 18 years ago. This question is for the respondent's birthday. In other words, since the respondent must be at least 18, when the birthday question comes up, I'd like the date widget to default to 2001 instead of 2019. Much more convenient for the user. I am thinking this must be an easy thing to do but I cannot find this in the documentation anywhere so perhaps it isn't. I can't even find a similar question on this forum and am sure this must have come up.

**2. What app or server are you using and on what device and operating system? ODK Collect v 20

3. What you have you tried to fix the problem?
I've t

4. What steps can we take to reproduce the problem?
None yet because I don't know if it is possible.

5. Anything else we should know or have? If you have a test form or screenshots or logs, attach below.
Apologies if this is obvious but can't seem to find if it is possible.

Forgot to add that even though the respondent must be 18, we allow a younger respondent to fill out survey in case some sort of follow up is needed, so I would like to DEFAULT to 18 and older but not RESTRICT to 18 and older.

You can put a date in the default column of the question. http://xlsform.org/en/#default has an example.

Thanks I knew it would be obvious and I was just missing it in the documentation. Thanks so much!!!

Craig