I have never paid much attention to what happens if my CD matures on a weekend/holiday but here’s my experience with three such CDs this year:
Ally Bank: CD matured on a Saturday. Set up instructions for the CD to be closed upon maturity and for proceeds to be deposited into my Ally Savings. Funds deposited into Savings on the Saturday.
Bank5 Connect: CD matured on a Sunday. Sent message requesting that the CD be closed upon maturity and for proceeds to be deposited into my Bank5 Connect Checking. Money (only a little over $500) was in checking account on Monday morning.
All In CU: One of my Smart Start CDs matured today, Saturday. Sent message yesterday requesting that the CD be closed upon maturity and funds transferred to another existing Smart Start CD. CSR replied to say that this will occur next Monday because the CD matures on a Saturday. I assume there will be no interest earned this weekend but am not worried as the amount is de minimis.