Why a 58 hour event?
Due to the duration of this event, there are more playable hours in some regions (Americas) than in others. Why has Niantic decided it? Why not a 48 hour event?
Answers
I'm not sure America's get more "playable hours".
Eastern Time zone (GMT-5) is where a large proportion of the Americas live. 4pm start time to 2am end time leaves us with more unplayable hours than Asia (4am start to 2pm end or better for GMT+7 or higher). Europe around GMT 0 (9pm start to 7am end) gets the shortest stick.
However when you look at community days, Asia regularly gets the short stick with server issues and bring a guinea pig.
When you look at daily raids, the Americas get the short end of the stick with raids ending at 6:45pm (meaning most weekdays you get about 45min to do a raid, with the average person finishing work between 5pm-6pm and getting home around 30-60min later).
Europe has had it great in contrast, so a shortened weekend may seem unfair to them but really there's no pity here :p
It is what it is. Every one will have at least two daytime periods to do the event, as well as a 3 hour window with the bonuses. If you live in Australia or Africa, the hours of starting and ending might be inconvenient, but you'll get your two days.
Of course, if you don't like it, e-mail Niantic and ask them for a refund for the money you paid for the event, ....
Seriously, it's a bit random, but everyone will get some good hunting time.
If you live in a safe area. I can play whenever I want, but I know there are more than a few areas out there where you don't want to go out at night with a cellphone in your hand and not paying full attention to your surroundings.
Another thing is of course the temperature for some areas. At night its colder, and there are much fewer buildings open where you can go warm up if you don't have a car.
For me personally this event isn't good enough that I'd sacrifice my sleep schedule for it. I'd consider it if the dust bonus lasted through the entire event.