I've noticed that many microwave instructions now call for a heating time of 1 minute 30 seconds. I think this is fairly recent thing (last few years) as I recall seeing instructions calling for a 90 second time. It's not any big deal, but it is a curious shift. Is 90 seconds now somehow nonstandard? Is it like an improper fraction, being over a full minute but all in seconds? Or is it that a new generation of instruction writers or rather those who approve them, has decided that "1:30" makes more sense with numeric keypads than "90" which is one less keypress? They mean the same thing. All the microwave ovens I've encountered deal with 90 seconds just fine, so not only do they mean the same thing but they have the same effect. It's hardly as if 1:30 would have been a problem setting the timer on the older twist-knob timers of earlier microwaves. Or is there now an assumption that people have trouble with 90 seconds instead of 1 minute 30 seconds?