What year is the Unix epoch — "time zero" for Unix timestamps — and how do you peg it?

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. Peg the year 19 · 70 → tub · case: a travel case floating in a bath tub. (A signed 32-bit counter of those seconds overflows in 2038 — the "Year 2038 problem".)