Keeping Time in Epoch Seconds

post by Gordon Seidoh Worley (gworley) · 2022-09-10T00:28:08.137Z · LW · GW · 2 comments

Unix-like computers keep time in seconds since the Unix Epoch—the 0 second, which is set to midnight, January 1st, 1970, Zulu/UTC. We call a particular second since the Unix Epoch a timestamp.

Keeping time this way is pretty handy, but looking at a long string of numbers is hard to parse. What to do?

Right now, as I'm typing, the current Unix timestamp is 16'62'7'68'531. See how I put those ' in there? That's how I try to break up the number into parts to make sense of it.

Starting from the right, the two rightmost digits make up what I think of roughly as a Unix minute, but rather than 60 seconds it's 100, so that's $1\frac{2}{3}$ standard minutes. One more unit over and we get the Unix hour, which is about a quarter of a standard hour long at 1000 seconds or $16\frac{2}{3}$ standard minutes.

Calling 1000 seconds an hour might seem confusing, but the purpose of hours is to have a convenient unit for dividing up days, just like minutes are a convenient way of dividing hours. Speaking of which, 100 Unix hours equates to 1 Unix day, or $27\frac{7}{9}$ standard hours. This is a bit longer than a standard day, but since some people seem to operate on 28 hour days anyway, they might find this appealing.

So that takes care of the 5 rightmost digits: 3 to track the seconds and minutes within an hour and 2 to track the hour within a day. The 6th digit from the right tracks the day of the Unix week, which is 10 Unix days, or $11\frac{31}{54}$ standard days. It's a bit longer than our standard 7 day lunar weeks, but 10 day weeks were good enough for the ancient Greeks, so they're good enough for Unix nerds.

Since months are tied to the cycle of the moon there are no real months in Unix time. Instead 100 weeks make up a Unix year, which is approximately 3.17 standard years long. If it helps, though, a tenth of a Unix year is about three and a half months long, so you can think of each ten-week as like the three month quarters or seasons we informally divide our calendar by.

Now we've accounted for all the digits. If we break down my example timestamp of 16'62'7'68'531, we can say that it was the 31st second of the 5th minute of the 68th hour of the 7th day of the 62nd week of the 16th year of the Unix Epoch. Breaking it down in a table:

16	62	7	68	531
year	week	day	hour	minute and seconds

Do I expect this to catch on? Not really. This is all just a bit of fun to make sense of Unix timestamps. I can't recall seeing anyone else try to break down the Unix timestamp like this into human-sized units—at best I've seen people talk about things like megaseconds, and I think I can recall others referring to 100,000,000 seconds as a Unix year—so I figured I'd share it. I've been using this in my terminal for years to help me make sense of what I'm looking at. Maybe you'll also find it useful.

2 comments

Comments sorted by top scores.