A Time Capsule for My Dad

My dad retired this year. We threw him a party at my parents' house - family and friends in and out all day, food, drinks, and a plan to end the evening watching England vs Norway in the garden, projected onto a big screen, because the World Cup waits for no retirement.

Somewhere in the middle of that day, between hosting duties, I built him a time capsule. Not a biscuit tin buried under the lawn - a digital one. Guests scanned a QR code, wrote him a sealed message, and walked away. Nobody can read what they wrote. Not my dad. Not me. Not until 27 March 2027, one year to the day after he retired, when the capsule unlocks and everything lands in his inbox at once.

This is the story of how that happened in the gap before kickoff, and why I think it's the best thing I've built all year.

It joins a small pile of things I have wired into that house: a CCTV watcher you can ask questions and an agent I can drive from my phone.

It Started With the Lights#

I'd already brought my laptop to the party, which tells you something about me, but in my defence it was for the football. I run a fair bit of smart home kit at my parents' place, including a Raspberry Pi home server and the garden lighting, and I'd decided the match deserved a bit of theatre: I was using Claude Code to wire the garden lights up to react to the game. Goals, big moments, that sort of thing.

Mid-setup, looking at the projector we'd rigged up for the match, a thought landed: this screen is going to sit here doing nothing until kickoff. Everyone my dad cares about is here, today, in one place. That combination of people never assembles again. Weddings, milestone birthdays, retirements - these are the only days you get the full cast, and mostly we let them pass with a card and a speech.

What I wanted was something like a guest book, but sealed. Notes to my dad that he couldn't read yet. Predictions about what his first year of retirement would look like, to be checked against reality later. The kind of thing that's a bit awkward to say out loud at a party but easy to type into your phone when nobody's watching.

And I had maybe a couple of hours before the football started.

What Got Built, and How Fast#

Two pieces, built in parallel with Claude Code doing the heavy lifting while I drifted in and out playing host:

• The capsule service - a small web app running on the Raspberry Pi at my parents' house. Scan a QR code, get a simple form: your name, your message, submit. The message is sealed on arrival. There's no read path for the contents. The only thing the system will tell anyone before the unlock date is how many messages exist.
• A TV app - a quick Android app for the Google TV Streamer driving the projector. Full-screen QR code, a line explaining what it was, and a live counter of messages submitted, updating on screen as they came in.

The counter was the sneaky bit. A QR code on a screen is easy to ignore. A QR code next to a number that just went from 7 to 8 is a social nudge: other people are doing this, quietly, and you haven't yet. Nobody announced it. Nobody was cornered and told to contribute. People just peeled off at their own pace, phone out, thumbs going, and wandered back to the party.

Watching that number tick up over the afternoon was genuinely the best part of the day for me. Every increment was someone - an old workmate, an auntie, a family friend - stopping mid-party to write something to my dad that won't be read for months. You could occasionally spot it happening: someone on a garden chair, typing with a bit more care than a WhatsApp message usually gets.

The Sealed Part Is the Whole Point#

The design decision I care most about is the one that sounds like a missing feature: I can't read the messages either.

It would have been trivial to give myself access. It's my server. But the moment the person running the system can peek, it stops being a time capsule and becomes a database with a theme. People write differently when they know a middleman might read it. The promise on the screen was that messages were sealed until March 2027, and the only way to make that promise honestly was to build it so it's true for everyone, including the person who built it.

So the contents are locked away until the unlock date. What I do have is an admin panel that shows the count and lets me trigger delivery manually - a belt-and-braces fallback in case the scheduled unlock hits a snag eight months from now. When the date arrives, the capsule emails my dad everything. He knows it exists. He knows roughly how many people wrote something. He has no idea what any of it says, and neither do I, and that shared not-knowing is a small ongoing pleasure. There's a thing waiting for him and all he can do is wait.

The Engineering Point, Briefly#

For the non-engineers: the remarkable thing here isn't any individual piece. A form that saves messages, a QR code, an app that shows a number - none of that is hard. The remarkable thing is the timeline. Idea to working-QR-code-on-the-big-screen happened in the gap before a football match, at a party, by someone who was also topping up drinks and being introduced to people.

That's what building with AI agents actually changes. I described what I wanted, Claude Code built it on the Pi while I hosted, I checked in between conversations to test and steer, and it was live before kickoff. Five years ago this is a weekend project I'd have started the Monday after the party, which means it never gets built at all, because the party is the whole point. The people were only there that day. Software that can be built during the moment can capture the moment. Software that takes a weekend captures a memory of it.

I've written before about agentic coding collapsing the cost of "should we build that?" decisions for side projects. This was the first time it collapsed the cost for something with a hard, human deadline of hours. It's a different feeling. Less like having a faster keyboard, more like having a workshop that runs itself while you're busy living.

March 2027#

The lights did their job during the match, England did theirs, and the party wound down the way good parties do. The capsule is still sitting there on the Pi, holding its messages, counting down.

On 27 March 2027 my dad gets an email full of voices from the day he retired - predictions that will have aged well or hilariously, in-jokes, and whatever people found easier to type than to say. I'll find out what everyone wrote at the same time he does.

If you've got a milestone coming up - a retirement, a wedding, a big birthday - steal this idea. The whole cast only assembles a few times. Give them somewhere quiet to leave something behind.