Time Capsule

Human beings are obsessed with leaving a record of ourselves so that future generations have some idea of what we were like.

Enter the Time Capsule, an object specifically designed to withstand the elements and hopefully will be dug up and opened some number of years after its burial. "Specifically designed" is the keyword here; anything from the past is obviously going to be of interest to an archeologist, but it only counts as a time capsule if the one burying it intended it to be as such.

Compare Write Back to the Future, which is essentially this trope meets Stable Time Loop. See also Dead Man Writing, Video Wills.

Examples of Time Capsule include:

Anime and Manga

Love Hina: As a youth, Keitaro buried one with Naru and Mitsumi stating his wish to go to Todai.

Film

My Sassy Girl: Gyeon-woo and the girl plant a time capsule. It contains the story of the girl and her previous boyfriend.
Knowing: A group of kids are told to draw what the future looked like; a creepy girl puts in a random string of numbers that Nicholas Cage finds after the school digs the capsule back fifty years later. The only problem: said paper predicts the end of the world.

Literature

In the Grandma's Attic series of books, a repair of the schoolhouse reveals a pioneer-style one of these, which dredges up old rumors about one of the townsfolk burning down the schoolhouse in the past.
The True Meaning of Smekday begins with an essay written by the protagonist to go in a time capsule.
The novel We Are Tam is split between two time zones: the 20th century, when a time capsule is buried, and the 25th century, when it is uncovered and opened.
The unexpected chance to recover a time capsule sets off the plot of Zombies of the Gene Pool.

Live Action Television

In one episode of Bones the Victim of the Week was found in a time capsule that some high school students had made 25 years previously, when those same students opened it up.
In an episode of CSI: Miami the fact that a graduating class' time capsule was being opened for their reunion was a plot point. The murder weapon was a bottle of booze that could only have been obtained by opening it early.
Degrassi did something interesting with this very recently, having High School sophomores dig up a time capsule with letters to their future selves written in seventh grade. This led to Wesley having a ~~mid-~~ ~~quarter-~~ one-sixth-life crisis and vowing to set a pogo-jumping record before his 16th birthday.
Head of the Class: the class put together a time capsule featuring a Music Video of them lip-synching to Timbuk 3's "The Future's So Bright I Got to Wear Shades."
The penultimate episode of M*A*S*H involves the 4077th putting one of these together.
- Incidentally, the show's cast also buried one of these in Real Life...but it was dug up by a construction worker shortly afterward.
In Monk, the burial of a time capsule ends up being the reason why the world's oldest man was killed. The killer put a confession to a previous murder inside, knowing it wouldn't be read for a hundred years. Then, the mayor told the world's oldest man that if he was still alive in five years, they would dig the capsule up and add to it.
Parks and Recreation: Plans for a Pawnee time capsule are derailed when someone demands to put in Twilight. Leslie calls for a town meeting to debate the matter, and everyone in town wants to put something in the capsule as well. In the end, Leslie just puts a video of the meeting, to show future generations how passionate the people of Pawnee were in 2010.
The kids put one together in an episode of Salute Your Shorts.
In Summer Heights High the teacher, Mr. 'G', buries a time capsule in which he discards some of the students' items in order to make room for pictures of himself.
Mighty Morphin Power Rangers has an episode where one of the classes the team attends prepares and buries a time capsule. It includes them stating their hopes for a bright future. Oh, the irony.

Newspaper Comics

In the Conchy newspaper strip, the characters accidentally dug up a time capsule marked "Do Not Open Till 1984". When they opened it, it was full of 1984 calendars.

Video Games

In one of the Harry Quantum games you have to manipulate a time machine to get a time capsule open to get one of the things you need in order to advance the plot.
In Alibi In Ashes, a clue to a long-ago crime turns up in a time capsule that was hidden in the building Nancy is suspected of burning down.

Web Original

One Strong Bad Email from Homestar Runner was about Strong Bad making a time capsule out of a giant medicinal pill, which is then uncovered by Stinkoman and 1-Up in the "20X6" future.
The MSPA fan adventure The White Depths has a literal example in the ship fridges, that actually stop time inside when closed. The meat is still fresh after eight millennia.

Western Animation

The frog in One Froggy Evening was found in a time capsule in a building cornerstone -- and dumped back into another one.