If you think crossing 180 degrees west longitude is crossing the international dateline you’d pretty much be wrong. The international dateline is a politically-hatched snake that slithers its way north-south across the Pacific Ocean. For example, in Tonga (officially, the “Kingdom of Tonga”) local time is GMT+13.  The higher math I know says that’s the same thing as GMT-12. Yes, but Tonga has very close ties to New Zealand. In fact, the shop and restaurant owners I got to know in Neiafu complained they couldn’t find local workers because they all went to New Zealand to pick fruit! Tonga wants to be on the same day as New Zealand so they invented GMT+13. 

Then you have places that aren’t satisfied with being an even hour difference from GMT.  They have half hour (Marquesas) or even quarter hour differences. There can be no rational explanation for this except sheer bloody mindedness. 

When I was hitchhiking around Africa in 1975 with backpack and guitar I got to know Swahili time in Kenya, on the equator. Zero o’clock was when the sun rose, consistently at about the same time. I remember bus schedules written in chalk on blackboards listing departures in Swahili time, which itself was an optimistic fiction because a bus rarely left until it was full of people, luggage, livestock, etc. It would drive all over town scooping up willing passengers to fill it.

On the boat I keep clocks and the log in GMT, except my watch which is set for my best guess at a local time. The weather forecasts are all in GMT so I need to convert to a local time to understand if the bad weather is going to hit me in the middle of the day or the middle of the night. Otherwise, it doesn’t matter much what time it is. The sun comes up then goes down, called daytime, the rest being nighttime which is routinely forecast to be dark. Then there’s the morning you wake up and realize it’s been tomorrow since yesterday. 

I never flew on the supersonic Concorde but I’m told you could take off from Paris at 10 am and arrive in New York at 9 am.  If you kept going around the world that way you’d never get old.  We need to bring that back.