March 13 or March 16 2020 ADP refund date

Which date is the actual final date to make the refund sans penalty?

Also... Folks gonna be mad with their refunds with the market correction

Neither... deadline is 15th ?

Here’s a 2009 discussion:

https://benefitslink.com/boards/index.php?/topic/40926-march-15th-deadline/

And 26 C.F.R. § 301.7503-1

https://www.ecfr.gov/cgi-bin/text-idx?SID=433ece255a30fe50ebca570ba8867b22&mc=true&node=se26.20.301_17503_61&rgn=div8

RatherBeGolfing’s observation isn’t idle, I once worked on a business deal in which my client obtained a national bank’s acts on a Saturday.

Is it not noon on the 16th?

I may sound like I'm trying to be a wise guy, but does the Code define half a month legally? 

I honestly would think an 11/30 year end plan might have a 2/14 deadline (noon on the 15th this leap year)