Anime seasons are generally 12/13 episodes long. There are quite a number of exceptions though, where more or fewer episodes are fitted into the same timeslots. Most notably, however, a season can have 11,12 or 13 episodes a season. I've seen this discrepancy occur regularly.

I would have thought that keeping the episode amount standard is good for keeping the seasons aligned — 52 weeks in a year / 4 seasons in a year = 13 episodes per season. The variant I see most is 12 episodes at a time or 12 episodes with a bonus DVD-only OVA. What do they do with the 1 week gap?

Do stations plan their seasons far enough in advance to make it even out overall? What if a show is cancelled?

Why does this anomaly exist? Surely it makes it awkward to schedule TV.

  • 2
    In my little experience, I noticed 12 episode long series rather than 13, just like you said before your edit
    – Ikaros
    Dec 14, 2015 at 18:51

3 Answers 3


This seems to happen in most regions. The typical reasons I've seen given are:

  • shows don't all start on the same day or even the same week
  • sometimes airtime slots are occupied by sports, seasonal, or other non-regular programs
  • networks may choose not to broadcast new episodes on holidays with historically low viewership
  • shows are sometimes only given an awkward number of slots like SuperGirl here.

I would also hope that some studios choose to show more or less episodes to ensure they have the right pacing and tell the whole story without an obnoxious amount of filler.

I imagine networks know pretty far in advance what their lineup will look like. Pilot episodes or other proposal material is submitted to the network far in advance for them to review before agreeing to broadcast. It is also important to remember that a large portion of every day's slots belong to re-runs so cancellations just call for more of those.


Actually, anime airing is usually divided in 4 "seasons" each year, following the earth's seasons. TV schedules get defined only close to the start of next season, and usually there are shows which were supposed to air that won't or they might get delayed.

Also, most of the time shows don't start airing on the same day/week within a season, and might get a one-week break during the season (i.e. non-planned event on TV, holiday in Japan).

To answer your question, anime TV scheduling isn't done that much in advance, and is honestly a complicated mess. TV networks won't plan a year ahead because they still don't know which series they are going to air and when they will be ready, so having a different number of episodes per show doesn't really screw up their scheduling.

  • 1
    "A complicated mess" sounds much more realistic than "known far in advance"... :)
    – deceze
    Dec 16, 2015 at 6:39
  • Correction: while the names of the anime airing seasons are named after the four seasons, the actual scheduling is much closer to fiscal quarters
    – awsirkis
    Dec 11, 2019 at 20:18

As you say, there are enough weeks in a year for there to be four 13-episode parts. This is true, and each of these parts is a season. However, there aren't always exactly 13 days of each day of the week in season. For example, the summer 2016 season (July-September) will have 14 Saturdays.

As to why shows go for 12 or 13 episodes, it's generally something the anime production companies decide early on in creating an anime (a few months prior to the show airing). Different studios and shows will have their reasons, but either way, there we are. Unless we were there when the decision was made in some board room, we don't know why a show got 12 episodes over 13.

When the planned season where the show will be airing is about to start, the anime production companies will call the TV stations and ask for time slots. (Generally, TV stations themselves aren't involved in producing anime, only just putting them on TV.) For example, one will call to say "we want to air a show on Saturday nights at 24:30 for the next 12 Saturdays". Another will call asking "we want to air a show on Thursday nights at 24:00 for the next 13 Thursdays". Whether or not they get the slot depends entirely upon whether or not someone else took it yet (and if the price for the slot is worth it).

Anime TV scheduling is competitive, as is a number of things in the anime production world. Anime production companies will try to be as quick as they can about getting a TV slot, but it usually isn't until relatively close to the start of the anime season that TV stations get a full schedule figured out. TV stations can count on their slots being filled, though, with the wide amount of anime coming out each season nowadays (and they can always rely on reruns otherwise).

So, to sum it up, anime production companies know from early on how many episodes they want. How they decide that is dependent upon the show. When it comes to the TV stations, they just offer up the time slots, that's it. The anime companies take them as soon as they can, for as many nights as they want them.

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