How long should a time capsule stay sealed?

What is the best length of time?

Match the wait to how much you want to be surprised and how much you can maintain. A year is short enough that you remember sealing it and long enough for real change. Five years is long enough to feel like a different person. Ten years starts to depend on devices, backups and your own habits surviving.

People tend to overestimate how well they will feel about the future and underestimate how much the small things will have changed, a pattern described in the Wikipedia article on affective forecasting. A capsule is a way to check your forecast against what happened.

What about the famous century boxes?

Public capsules go much further than a personal one. The capsules from the 1939 and 1965 New York World's Fair are meant to be opened in the year 6939, according to Wikipedia. They are designed for strangers and kept by institutions, with documentation on how to find them.

The lesson is practical. A long wait works when someone is responsible for it. A capsule is easy to lose when nobody records where it is, and the time capsule article covers the idea of a plan for finding it. A personal capsule has no institution, so you are the institution.

What goes wrong as the years pass?

Only the last one is unusual. Sealday's lock depends on the drand network continuing to publish. If it stopped for good, a capsule you sent could not be opened, while your own capsules have a spare key in the iPhone Keychain that works after 72 hours without the beacon once the open date has passed. The details are on the time lock page.

• Your phone is replaced and the capsule is not on the new one.
• You forget the app or the date.
• A file format stops opening.
• You are no longer the person who cares, and the capsule stays unopened.
• The service that holds it shuts down.
• For a time-lock scheme, the network that publishes keys changes or stops.

How do I make a long wait safer?

1. Put the open date in two calendars and tell one other person.
2. Export a vault file from You > Backup and restore and keep it in two places that are not the phone.
3. Turn on iCloud Backup, so the app comes back with the iPhone.
4. Re-export after you add new capsules.
5. Check once a year that the file still opens a list of capsules in the app.

What does a sensible plan look like?

Here is a plan that has worked for people who like to keep things simple. Seal a New Year capsule every December with ten guesses. Seal a birthday capsule with a letter and a photo. Once, at a turning point such as a move or a new job, seal a five-year capsule. Export a vault file after each one.

That gives you two quick surprises a year, one long wait and almost no maintenance. If you only do one of these, make it the New Year capsule, because the date is hard to forget and the guesses are the most fun to grade.

Should I make several short capsules instead of one long one?

Usually yes. A one-year capsule every birthday gives you ten surprises in ten years, each with its own guesses to grade, and a series teaches you more about yourself than one distant message. The yearly ritual in Sealday, a New Year or birthday capsule, is free and does not count toward the three waiting capsules on the free plan.

If you want one long capsule too, keep it small: a letter, a photo, a voice note. You will not read thirty items when you open it, and the shorter the capsule, the lower the odds that something is lost.

Does the wait change what I should write?

Yes. For a year, write about routines and guesses. For five, describe your circle and your plans. For ten or twenty, explain things you would otherwise assume: how to say the names of your friends, what the jokes mean, what prices and technology are like. Future you will not need to be told the obvious, but will love being told the obvious. See time capsule ideas for adults for what to add.