Time Locked Town

1. The Point of Focus

The Time Locked Town has a singular day or week as it's perpetual focus. It isn't magically trapped (though it could be) and it is more a function that the specific holiday or specific day is of major local importance. Halloween Town, and the North Pole would represent magical time locked towns.

In real life, the city of New Orleans is almost always revolving around Mardi Gras, building up to it, reveling in it, recovering from it, and then preparations start again. Likewise, the cities of Gatlinburg and Pigeon Forge are both perpetually focused towards Christmas, with the Christmas light season running from November to January, and there are Christmas themed stores that are open year round,

2. Holiday Folk

Everyone in a time locked town knows that the importance of the holiday, but other than logistics and whatnot, no one talks about the WHY of the time locking. Likewise, most of the local businesses will be in some way themed to the Holiday, since in truth, it is never really not being celebrated. To outsiders, the locals will have an obsession with said holiday, a queer manic energy, and a cultish devotion.

The series Happy! featured a strip club called The North Pole, where all the dancers were dressed as elves and almost all of the patrons were mall and street corner Santas.

3. The Holiday Society

The city planning and display will have some sort of demi-secret council or society that oversees the perpetual celebration of the holiday. Newcomers have to be vetted, and plans for expansion or renovations have to be approved by the society.

4. Holiday Occurrences

The holiday isn't an abstract, it is something that very directly affects the town. More often than not, this is just a social and economic impact, so that tourists are drawn to the holiday atmosphere even if the rank and file locals are over it. In a more magical setting, holiday magic and miracles can occur in the time locked town more than anywhere else. 

Holiday specials are ripe with this, with visits to Christmas themed destinations revealing the meaning of Christmas, or a Halloween town actually being haunted. It is never dull.

5. A Place Apart

The time locked town is a place apart from the regular world. The mundane demands and trivialities out the outside world aren't welcome. High tech devices are prone to failure, or are cut off from signal. There are no conference skype calls in Christmas Town. Telephones, flashlights, and car batteries are notoriously faulty in Halloween towns. The Time Locked Town is a consensual reservation away from modern life.

6. Holiday Relics

There will always be something significant to the holiday located in the time locked town. This might be something like an actual physical relic, or actual remains where a person deeply associated with the holiday is interred, but it is more common that something of deep and great holiday importance happened in the town. The site of the first celebration, the site of where the holiday was saved, or that even people who are responsible for the celebration and the holiday itself reside there.

The Chilling Adventures of Sabrina features Greendale, an innocuous generic American town that is time locked to Halloween, and is a huge focal point for the Satanic Church of Night. Hits all the high points easily.

7. Overkill

Halloween or Hell-oween locked towns can be highly fatal, other holidays, not so much. The threat presented by the non-lethal holiday is that the visitors to the time locked town might decide to never leave, to give up their outside lives, outside families, and retreat into the holiday retreat, forever. While living in a Christmas Town or Easter Town or Spring Break resort might seem like hardly a threat, the harm isn't felt by the taken, but by the friends and family who've lost someone to the town.