What are the instances that there is no manga (like Naruto, Bleach and One Peace) release? Are there certain events that prevent them from releasing? Then what are these events (aside from taking a break)? Is there some sort of calendar of events for this?.
You have to understand that the manga industry is in fact an industry and normal industry situations happen.
The reasons behind a manga not coming out can be the same reasons some shop or company does not work at certain periods of time, but more specifically I've seen the following:
- There is a public holiday for that period in the country of the publishing (e.g. Golden Week).
- The author of the manga is taking a break after a two-chapter release. (Which basically means that the author already did this weeks job last week)
- The author is on vacation.
- The author is on an unpaid leave due to reasons of his concern.
- The author is sick and cannot work due to that. (Pretty much calling in sick, in layman terms).
Any other reasons a normal person may not be able to work at a job all also apply here. If by chance there is a public holiday but a chapter still comes out, chances are the author prepared the chapter beforehand, and is enjoying the holiday like everyone else, although it appears that he was "working" that week.
As pointed out by Miharu in the comments below, there also might be a rare situation where a manga which is based on a currently airing anime has caught up to the anime and therefore might take a break to let the anime progress a little further. (Personally I haven't seen this phenomenon though.)
The most typical reason is a scheduled vacation. Out of four weeks the year, Japan celebrates major holidays and festivities. Many schools take the week off as a holiday.
At the time of you question is the holiday called "Golden Week." These are the only times that the mangaka can take a scheduled break without taking a hiatus (e.g., taking off the next issue). They called preceding issue (before the break) is a "double issue." Now you may think that a double issue means that since the magazine is meant for a 2-week period, the contents are doubles. That's not the case here. What's implied is that there will be no Weekly Shonen Jump issue in the following week.
There is no Weekly Shonen Jump the last week of December (end of the year; Christmas), 2nd week of January (New Years holiday), first week of May ("Golden Week," a series of holidays), second week of August (Obon).
Here is what I found out, something called a "Golden week".