Build with LOCKRA.
Timelock in a few lines.

const capsule = await seal('I will ship v2 before March', {
  unlockAt: '2027-03-01T00:00:00Z', // or a Date, or epoch ms
  // unlockIn: 3600,                // …or seconds from now
  label: 'Promise',                 // public title, tamper-proof
  by: '@lockra',                    // public author, tamper-proof
});

capsule.link;     // share this
capsule.unlockAt; // Date
capsule.round;    // drand round that unlocks it

const r = await open(capsule.link); // a link, a token or the capsule object

if (r.status === 'sealed') {
  console.log(`Still sealed, ${r.secondsLeft}s left`);
} else {
  console.log(r.message, r.sealedAt);
}

// Or wait until it unlocks
const opened = await open(capsule.link, { wait: true, timeoutMs: 60_000 });

inspect(link);
// { round, unlockAt, unlocked, label, by, wallet }

import { readFile, writeFile } from 'node:fs/promises';
import { sealFile, openFile } from 'lockra-sdk';

const { capsule, file } = await sealFile(await readFile('report.pdf'), {
  name: 'report.pdf',
  type: 'application/pdf',
  unlockAt: '2027-01-01T00:00:00Z',
});
await writeFile('report.pdf.lockra', file);

// Later
const r = await openFile(await readFile('report.pdf.lockra'));
if (r.status === 'opened') await writeFile(r.file.name, r.file.data);

import { walletMessage, attachSignature } from 'lockra-sdk';

const signature = await signer.signMessage(walletMessage(capsule));
const signed = attachSignature(capsule, {
  address: await signer.getAddress(),
  signature,
});

signed.link; // shows "Wallet-signed by 0x…" on lockra.buzz

import { open, LockraError } from 'lockra-sdk';

try {
  await open(link);
} catch (err) {
  if (err instanceof LockraError && err.code === 'TAMPERED') {
    console.warn('Someone edited this capsule.');
  }
}