Ruby code

[wmute]

I wrote my first actual piece of Ruby code, recently. My watch has (as well as the usual hands) a hand that makes one sweep every 24 hours, and is currently set to London time (BST, at present, but for the sake of argument, I am considering it as GMT / Zulu time). I was curious as to when it and the normal hour hand would line up, and as I was in

Comments

[mollyemo]

I think it's once a day, 1400 BST and 7am EST. The once a day seems obvious enough, but I'm not terribly sure about the time...

[wmute]

You're certainly on the right track - except that the difference between EST and BST (or between EDT and GMT, as I'm approximating it - I should have done this in the winter, really) is 5 hours, not 7. But other than that, you're getting there.

[mollyemo]

Stupid military time confusing me. Never ask me to use a 12-hour and 24-hour clock at the same time ;-)

Is it 1000 and 5am, then?

[wmute]

It is.

More generally, it will be when the time since local midnight is equal to the amount of time you are behind GMT. For example, Moscow is +0300, which means that GMT is 21 hours ahead (as we aren't concerned with dates), so that 21:00 (9pm) in Moscow is 18:00 in London.

In essence, if the local clock begins at midnight, the GMT clock begins x hours ahead, but then advances at half the rate of the local clock, so that after an additional x hours, the local hour hand shows x o'clock, and the GMT hand shows 2x o'clock, which puts them at the same location.

I hope that makes sense. It does in my mind, but I'm not sure I've explained well.