Those of you versed in video game history will be aware of a story relating to the astonishing popularity of Dragon Quest, one of Japan's most beloved RPGs. Back when the series was just starting out on the Famicom, kids and adults alike would bunk off school or work to buy it and spend an entire day playing. The resultant "sick day" epidemic was apparently so bad that it actually had an adverse effect on the Japanese economy (or so the legend states).
Things became so dire that a law was passed in Japan which forbade Enix from releasing a new Dragon Quest game on a weekday - and that tradition continues to this very day. Many have since accepted the "Dragon Quest law" as solid fact, but here's the rub - it's a myth, although some elements are true.
Enix did begin to release Dragon Quest games on a Saturday, but not because it was told to by the Japanese government - it came to an agreement with Nintendo and decided to shift the release day voluntarily.
So there you have it - another urban myth is squashed.