Why since the dawn of JPMMO time...

[Riko_Futatabi]

...has the maintenance time posted in GMT timezone ALWAYS been one hour off?

Example: It's posted on the site and in-game as 8PM GMT start-time which really means 9PM GMT start time.

It's been over a decade and I'm sure most in this timezone are used to it, but why at least out of curiosity does this rarely say the correct time for GMT?

[Blackhalo]

Because it IS GMT, but you are now on Summer probably and therefore your time is GMT+1

[Bixby]

Yuuup. GMT is GMT all year round. If you observe daylight savings time (or whatever y'all call it there), you're technically on a different time (e.g. BST). Much like the difference between EST and EDT for those in the Eastern time zone in the US (including the part where people say they're on EST even during DST, when they're really on EDT).

They could post European times in whatever DST would be appropriate (the NA posts are always in PDT or PST as appropriate), but I'm not sure how standardized it is over there. Does every country do DST on the same dates etc.?

[Cassandaria]

This is a constant with any mmo that uses a raw time zone. It's not just JPMMO's that do this. They are using GMT, not GMT +1, so the times will be different dependent on if your location observes daylight savings time or not.