This guide explains time capsules in plain language, with the exact figures and how to work them out yourself.
Last updated: August 1, 2026
A time capsule is scheduling at its most audacious: a container, a collection, and an opening date chosen by people who will never see it honored. The modern tradition crystallized in the late 1930s, when Westinghouse buried a torpedo-shaped capsule at the 1939 New York World’s Fair — microfilm, seeds, a slide rule, messages from Einstein — inscribed to be opened in 6939, five thousand years on. A companion joined it at the 1964 Fair, and granite markers above them patiently state the appointment.
The grandest commitment lies beneath Oglethorpe University in Atlanta: the Crypt of Civilization, a sealed chamber the size of a room, stocked between 1937 and 1940 with everything from recordings and appliances to a device for teaching English to the finders — because its opening date, calculated to sit as far in the future as the earliest Egyptian calendar dates lay in the past, is the year 8113. A steel door was welded shut in 1940; the university’s only task since has been remembering.
The habit is ancient in spirit — foundation deposits under Mesopotamian temples, relics and documents in building cornerstones — and universal in practice: schools bury shoeboxes for reunions, cities seal centennial vaults, families lock letters for children’s future birthdays. The International Time Capsule Society has estimated thousands upon thousands lie buried worldwide — and that most are lost, their locations forgotten within a generation, which is itself a lesson about time: the hard part isn’t sealing the box, it’s transmitting the appointment.
Two capsules have already left the planet. The Voyager probes, launched in 1977, each carry a Golden Record of Earth’s sounds, music, and greetings in dozens of languages — addressed to any finder, deadline never, drifting toward interstellar space as the longest-scheduled message ever sent.
Digital versions now let anyone email their future self or lock files for decades, trading buried steel for scheduled delivery — the same wager that a future someone will be there to open it.
Every capsule is ultimately a bet on the calendar’s continuity — that 8113 will mean something to whoever reads the marker. The date mathematics that make such appointments possible run daily, at humbler scales, in the calculators at itsdately.com.
The failures teach as much as the monuments. Capsule hunters estimate the majority of buried capsules are effectively lost — paperwork discarded, landmarks demolished, coordinates never written down — and famous embarrassments abound, like the car buried with a Tulsa courthouse capsule in 1957 that emerged in 2007 as a rusted shell, its vault having flooded within years. The professionals’ checklist is unglamorous: argon-purged stainless steel, acid-free contents, no batteries, no rubber — and above all, multiple recorded custodians of the date and place.
The deepest versions abandon retrieval altogether: seed vaults in Arctic permafrost, million-year nuclear-waste markers designed to warn readers of unknown languages, and genome archives etched in glass — capsules addressed not to a date but to whoever, and whatever, comes.
Whether steel in Georgia or gold on Voyager, every capsule performs the same act of faith the calendar itself performs daily: treating a future date as real, addressable, and worth preparing for. Sealing one is simply scheduling, done with ceremony.
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Related on itsdately: John Harrison and the Clock That Solved Longitude · A Short History of the Wristwatch: From Jewelry to Trenches to Quartz · How Sundials Work (and How to Read One Correctly)
Further reading: Encyclopaedia Britannica — Clock.