The framing borrows from how fans periodize artists' careers by album. Applied to regular life, it adds narrative weight and humor: a breakup becomes a "villain era," a quiet month becomes a "homebody era," learning to cook becomes a "domestic era." Declaring the era is half the fun.
It is a workhorse caption format because it announces change while keeping it light. Creators use era-framing for rebrands and new content directions ("entering my longform era"), and comment sections diagnose other people's eras for them. The ironic register — "in my walking to the fridge era" — is equally common.