Birthday was 5/14 -- had flights on 5/13 (CLE-IAD, solo - business meeting in Richmond and picking up my wife from our place in DC) and 5/14 (IAD-ATL, with Ms. LincolnJKC).

"Everyone" in CLE extended personal wishes (which I appreciate and was definitely non-corporate since I see them more than some of my real coworkers )

CLE-IAD crew presented everyone in the F cabin with a handwritten card mine included a "enjoy your birthday tomorrow" which I thought was a really nice gesture asked how old I was going to be before suggesting "21?" ("For17th time " was my response ) and a PA on arrival.

IAD-ATL... not a word at check-in, inflight, or on arrival (and one of the least pleasant TSA experiences in recent memory, but that's not UA's fault)... I guess whatever the "this passenger has a birthday coming up" flag is gets reset as soon as the first flight 'in window' passes.