Because everything than happened between 4x22 and 5x06 happened in a month or a month and a half.
The characthers said several times, like Diane saying it’s been three weeks since Alicia stopped decoridng. Or the countdown for Cary and Alicia to leave it was 4 days, but 3 episodes took place in those days.
So it was still may or july and Zach was still in high school.
Then they made the time jump in the episode called “The Next Month” and another time jump to catch up with the real world and the holydays. So Zach is college now, they just haven’t show us.
No, because we’ve seen him wearing the school uniform.
The writers just decided that they wanted F/A to throw a Christmas party and didn’t care about screwing up the timeline.
They do this all the time. Between season 2 and 3 for instance: it was the next day, but somehow Alicia had time to go to the hairdresser before work (unless she cut it herself when she came home after the hotel, which…would make sense for how awful those bangs were).
Yes, we’ve see him wearing his school uniform last time in 5x07 “The Next Week” which meant that it was still may or maybe june.
So “The Next Month” will be in August 2013
"Whack- A-Mole" and "The decision tree" are in november and december.
All the writters did was encapsule the first 7 episodes of the show in a month (May 2013) of the characthers lives. And then they moved the story to be current with the real world events (December 2013)
Although with the writing in this show, it doesn’t really matter.
But actor’s hair is always funny. Specially when they are on vacation and get a haircut that doesn’t fit they character and everybody just ignores it and moves on.
Makenzie Vega was blonde for season and nobody say anything.
Or sometimes they got sun tan