1970 → tub · case.

The Unix epoch is 00:00:00 UTC on 1 January 1970; every Unix timestamp counts the seconds elapsed since that instant. The date was a pragmatic, round choice made at Bell Labs in the early 1970s — close to when Unix was being written, and easy to reckon from. (An earlier Unix used a 1971 epoch that ticked 60 times a second, but a one-second tick counted from 1970 was cleaner and didn't overflow so fast.) Because the count was stored in a signed 32-bit integer, it overflows on 19 January 2038 — the "Year 2038 problem" — which modern systems dodge by widening the counter to 64 bits, good for another 292 billion years. Peg the year 19 · 70 → tub · case: a travel case floating in a bath tub.

Go deeper:

• Crash Course Computer Science — full series (PBS) — 39 short episodes tracing this whole timeline, from early computing through transistors, ARPANET and the World Wide Web. A great overview of every year in this deck.

1969 → tub · ship.

On 29 October 1969, ARPANET — funded by the U.S. Defense Department's Advanced Research Projects Agency — sent the first host-to-host message between Leonard Kleinrock's lab at UCLA and Stanford Research Institute. The operator typed "LOGIN"; the link crashed after the first two letters, so the Internet's first word was an accidental "LO". ARPANET pioneered packet switching — chopping messages into addressed packets routed independently — the idea that underpins all networking today. The same year, after the failed Multics project, Ken Thompson and Dennis Ritchie began building Unix at Bell Labs on a spare PDP-7. Peg 19 · 69 → tub · ship: a toy ship in a bath tub.