I've started to notice lately that the vast majority of anime (that I can find, anyway) seems to have opening (OP) and ending (ED) sequences which are 1 minute and 30 seconds long.
Some examples (though I'm sure there are lots that I haven't covered):
- Fullmetal Alchemist: There are 5 OPs and 5 EDs, all of which are 1:30 long.
- Digimon Tamers, Steins;Gate: Both OP and ED are 1:30.
- GaoGaiGar and Neon Genesis Evangelion: The OPs are 1:30 long, though the EDs are only 1:00 in duration.
- Cardcaptor Sakura: The OPs are 1:30, did not check the ED durations.
There do seem to be some exceptions (again, far from an exhaustive list):
- One Piece: Though some episodes fit this pattern, others have 3-minute OPs and no EDs. (The combined duration is still the same, though.)
- Akagi, Kaiji: OP is shorter than 1 minute.
- Ga-rei: Zero, Aria: During the OP or ED music (which is 1:30 long), things unrelated to the OP/ED sequence happen (like actual parts of the episodes).
These lists are just examples of each, and don't really show that the vast majority of anime (I would wager 90% or higher) seem to follow the 1:30 OP/ED "rule".
It is worth noting that most American series have openings which are 30 seconds or 1 minute in length; Family Guy and the Sonic the Hedgehog cartoon are examples of this, though there are far more.
When did the 1 minute 30 second duration of OPs and EDs start to come into popularity, and is there a particular reason why they did so?