Why is Kabul, Afghanistan 4 hours 30 minutes ahead of GMT?

They’re not alone. There are other time zones on the half hour; Newfoundland time for one. There are even some time zones that are on the quarter hour. The country of Nepal is one of those.

Is there something about the curvature of the earth that makes this seem like a good idea? Do countries arbitrarily decide what their time is going to be, or is it assigned to them?

Good question. I’m guessing some body was used to set boundaries but I would imagine the country involved would have the final say on what time zone it’s in. But I really don’t know the answer there. I do know there are parts of Maine that cross into Atlantic time but that they don’t recognize it and only subscribe to Eastern time. Same thing with Nome, Alaska which crosses over into the Samoa Time Zone but they use Alaska time as the rest of the state does.

I could see deciding that a boundary for a time zone should follow a state or county boundary. Indiana used to be horrible with time zones and daylight savings time.

Countries can arbitrarily decide what time zone to be in. Soviet Russia, for instance, tried to make the time the same across their entire territory (which now takes up 9 or 10 time zones). Arizona doesn’t honor DST, and neither (I think) does Hawaii.

For most of human history, the time on the clock mattered not at all. It’s really only been since the advent of mass transportation and, even later, television, that what time it is took on such great import.

My theory on Afghanistan is that they want the extra half-hour to maximize daylight for governmental operations. The majority of Afghans may or may not own a clock. And the US military and its contractors are operating on their own anyway, so they won’t be terribly affected.

Because of this time different, will it stay or conform sometime?

I am still asking why this shouldn’t to standard instead of the half hour different???