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Every year, Jump has 4 scheduled breaks. Though there can be irregular breaks, they are incredibly rare - iirc the last one was during the Tohoku earthquake and tsunami in 2011. Individual series can take a week (or more) off any time, usually because the mangaka need extra time for research or have health issues, but the entire magazine normally only goes on break when there are national holidays.
These are the approximate times, the specific dates are different every year, naturally.
Issue #04-05 -> third week of December
Issue #06-07 -> first week of January
Issue #22-23 -> last week of April
Issue #36-37 -> first week of August
As you can see, the issues all have a double number, hence why we call them double issues. We've tried explaining how this all works many times in the past, including drawing sketches and whatnot, but
many some people still misunderstood what double issue means, so I figured I'd give it one more try here.
There's 52 weeks in a year and WSJ is a weekly series, hence every issue is labelled with a number. However, they don't correspond with the actual weeks of the year. WSJ's year begins in December. Don't ask me why. At the time of writing this, December 18th, we're already on Issue #4-5. Also, have you ever noticed how at the end of some monthly series, like Claymore, it says "To be continued in the March issue" or something along the lines? Well, the March issue is released sometime in early February and just covers the period until March.
In order to not break the naming pattern, the issues preceeding a holiday receive two numbers, covering for two weeks effectively, they are what we call double issues. Now, I know it may seem natural to assume that they also must contain two chapters of everything to 'make up' for the lack of Jump in the following week - but that is not so.
This is something that really bothers me when people complain about it. "Why don't they draw a 2nd chapter!" Because it's a lot of work, obviously. It's almost like asking why they don't just draw the whole story in one night and get over with it already. Why? Because they're 'only' human, and already work crazy hours. Because you can't force creativity, and because they also have a right to have some time off with their families. Most fans are completely understanding of this though, which is much appreciated. :)
So yeah, if it hasn't been clear yet - there's only one chapter in double issues, just like there's only one chapter in regular issues. Besides, if there really were two chapters of every series in Jump for those weeks, the already phone book like shape of the magazine would turn into something that could easily kill you if it fell on your head...
Now, let's see what to expect this year. Issue #04-05 was released today, meaning the following week there's usually no Jump. However, due to various circumstances, this rule doesn't always hold true during the Christmas holidays. In the past few years we usually got the next issue (#06-07) extra early, I personally expect it between December 26th and 28th, but take that as an educated guess, nothing's confirmed. If I remember correctly, issue #8 came out on January 15th last year, so there was quite a long break and it's likely to happen the same way this year again.
Finally, I'd just like to ask everyone to be patient. We have no influence on when chapters come out, but rest assured we always release them within hours after we receive them, even during the holidays. And about the long break, well, that's a yearly thing, unfortunately. Maybe we can collect a few great series as a community that we can recommend to others.
I'll begin - everyone who calls themselves a manga enthusiast should have read the Golden Age arc in Berserk!
PS: To answer some typical questions that follow posts like the one above:
Jump = Weekly Shonen Jump = One Piece, Naruto, Bleach, etc - for more info, google which series are in the magazine.
No, double issues really don't have two chapters in them. Yes, that sucks indeed.
No, we don't know when Hunter X Hunter will return yet. The rumors you heard about it coming back in December were fake.
No, you can't have my number or be my butt buddy.
No, Fairy Tail is not in WSJ, and I'm not 100% sure about its schedule, so I didn't mention it above. But the magazine it's in also takes a week off during the national holidays.