It wasn't until around 11:00pm that I noticed why: My phone thought it was the 28th again. It had registered as the 29th until at least 2:30am (I have the auto-dated PocketQuicken transactions to prove it), but then had set itself back to the 28th at some point.
My phone is set to automatically get the date and time from the network, so I suspected AT&T. A quick search for specs shows the date/time format has the month and month-day separated out, rather than rolled into a seconds-of-epoch format.
And rebooting the network connection after midnight got me properly set to March 1st.
So it looks like AT&T doesn't believe in leap years.
No wonder so many groups are pressuring to get rid of the leap second. Large, supposedly tested systems are having a hard enough time with an extra day every four years.
So many morons, so few shotgun shells...