What's the common duration for preschool in the east coast?

When I was a kid in the nineties. It was only a year. Around age 4. I didn't go by the way I went straight to K.

Somehow at a friend's office garden party, the zoomers (I'm a young millenial and single AF 😭) were saying that preschool were actually three years around age 2 to 5. Fellow baby millennials told me their kids went for two years, around 3 to 5.

What is going on 😭