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Comment by madcaptenor | Hacker News Reader

Interestingly, the date line wasn't always where it is now. For example if you look at the tz database it has Asia/Manila with an offset of -15:56 until 1844; that's because the Philippines were actually colonized from Mexico, so they kept the same day count as the Americas. (https://webspace.science.uu.nl/~gent0113/idl/idl_philippines...). But as they came to be more integrated with their geographical neighbors they switched to counting the days like them.

Similarly tz has time zones as far east as +15:13:42 for Metlakatla in far south eastern Alaska, until 1867, since Alaska was settled from Russia. I think these are basically the furthest east and west the date line ever went (although maybe the Russians made it further south and east along the west coast of North America?)

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> the Russians made it further south and east along the west coast of North America

This is why there is a Russian River [1] in northern California. One of its names is "Slavyanka River" which was given by Russians.

[1] https://en.wikipedia.org/wiki/Russian_River_(California)

I didn't realize Russia ever had made it past Alaska! The world would be a very different place if they were there a couple hundred years earlier.

And of course Manila is not the westernmost point in the Philippines. Wikipedia has local mean time in the Philippines going from -16:12 to -15:34 (https://en.wikipedia.org/wiki/Philippine_Standard_Time), although that assumes that the current Philippines have the same longitudinal extent as in 1844 - and I can't quickly figure out the history well enough to know if that's true.

Russian fur traders made it to what is now called the Russian River in northern California in the early 1800's, founding Fort Ross.

Of course! And it looks like the Spanish weren't north of San Francisco at the time, so the only people in the area using something resembling our current time system would have been Russians coming from across the Pacific.

So the easternmost "time zone" ever is at least +15:47 or so.

I thought historical data in the tz database was recklessly deleted a few years ago. (To my horror)

It wasn't! See https://github.com/eggert/tz/blob/main/asia

It was deleted from the default build of the timezone files but remains in the source tree; patches are accepted.

Choices have to be made for usefulness vs completeness vs size as it's quite likely that at least one and perhaps multiple copies of the database are present on any system out there running code in C that needs to know what time it is in human terms.

But if you're a packrat, you can include the extras in your build of the timezone data by setting PACKRATDATA=backzone during the build.

That's actually a total relieve. I must have misinterpreted this change when it happened.

> Interestingly, the date line wasn't always where it is now.

Different empires defined their own prime meridians (and thus implicitly their date line 180 degrees away) from the ~16th-19th century. Eventually in the late 1800s a conference was organized to pick one and since Britain was the center of commercial shipping (with all the concomitant infrastructure like Lloyds, project finance, Admiralty law etc) there was little dissent.

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