How can I programmatically set date field Month, Day, Year dropdowns in Paragraphs?
After trying just about every solution for the date I could find, I finally figured this out.

It seems that it doesn't even matter what the DB is wanting to save the date as. Looking in the DB, the date is being stored as Y-m-d without the trailing H:i:s. Most examples are saying that you need the full date in Y-m-d\TH:i:s format.

This particular dropdown widget for the date field wants only Y-m-d and I only found that out after trying to pass it all kinds of different date strings and it gave me an error message back about the format without the trailing H:i:s.

So all of that garbage that I tried to pass it earlier and formatting was way off. All I needed to do was this, and the paragraph saved properly and the form fields are reflecting the proper date now.

'field_program_year' =&gt; date('Y-m-d', strtotime('2011-11-12')),
'field_eligibility_range' =&gt; [
  'value'=&gt; date('Y-m-d', strtotime('2011-11-12')),
  'end_value' =&gt; date('Y-m-d', strtotime('2011-11-12'))
],