The singer-songwriter spent Tuesday -- the two-year mark in their marriage -- riding a bicycle around the affluent Long Island hot spot ... rockin' a pair of overalls with her entourage in tow.

J Lo accessorized with big hoop earrings ... though the jewelry that'll really catch people's eyes is the rock on her left hand -- yep, she's still got her wedding ring on.

Instead of hopping on a tandem bike with his wife, Affleck spent part of Tuesday at his L.A. office -- making it clear Bennifer didn't have their anniversary circled on their calendars ... and it ain't spurring them back to each other's arms.

In fact, neither acknowledged the day publicly -- no cryptic post on Jennifer's social media, but, at this point, that's no surprise.

We broke the story ... sources with direct knowledge say they're headed for a divorce -- and, the recent public listing of their home was the next big step toward a legal split.

BTW J Lo did post about Ben on Father's Day -- even though he'd already moved out by that point -- so, it wouldn't have been out of character for her to say something on social media.