[danjovic] came up with a nifty entry for our 2025 One-Hertz Challenge that lands somewhere between the categories of Ridiculous and Clockwork. It’s a clock that few hackers, if any, could read on sight—just the way we like them around here!
The clock is called Hexa U.T.C, which might give you an idea why this one is a little tricky to parse. It displays the current Unix time in hexadecimal format. If you’re unfamiliar, Unix time is represented as the number of non-leap seconds that have ticked by since 1 January 1970 at 00:00:00 UTC. Even if you can turn the long hex number into decimal in your head, you’re still going to have to then convert the seconds into years, days, hours, minutes, and seconds before you can figure out the actual time.
The build relies on an ESP32-S2 module, paired with a 7-segment display module driven by the TM1638 I/O expander. The ESP32 syncs itself up with an NTP time server, and then spits out the relevant signals to display the current Unix time in hex on the 7-segment displays.
It’s a fun build that your programmer friends might actually figure out at a glance. As a bonus it makes an easy kicking-off point for explaining the Year 2038 problem. We’ve featured other similar Unix clocks before, too. Video after the break.
I have to go finish my Epochalypse clock. Only 12.5 years to go.
Or four weeks, I guess, if I want to put it in the contest.
seems the time for C0FFEE is already over. Got to wait for DEADBEEF…
If I got it right that time was in 1952-04-14 15:27, at least in a UNIX system…
Nope. Unix timestamps start at Jan 1, 1970.
0xc0ffee would be Wed May 27 09:27:10 GMT 1970
Contrary to some beliefs, the universe existed before 1970. And timestamps were negative numbers. 0xDEADBEEF is -559038737 seconds, 17.7 years before 1970.
Hence the rollover concern for 2038, when the 32 bit number goes negative again, plunging us all back to pre-WWI.
55789A69
Or my personal favorite, ABAD1DEA.
The timestamp in the thumbnail pic:
$ perl -E ‘say scalar gmtime hex shift’ 0x68675a69
Fri Jul 4 04:36:57 2025
Even easier if you use a Cheap Yellow Display …