She obviously means 420. It's a number, what's so hard to understand ?

Ok.

When she posted it it was actually 4:20 EST

April 20th is international stoner day/international weed day. It's like a day where everyone celebrates pot and smokes it.

http://en.wikipedia.org/wiki/420_(cannabis_culture)

Apparently it got its start in the 60s or 70s. Students would always start smoking at 4:20pm after school had finished.

not most of the ppl completely missing the sarcasm in the op lmao

More like 420 years.

No. That means she's high and liking it.