Write them together, before the airport.
A year of distance starts with one bad drive to an airport. Before it, while you are still in the same room, write each other into next year: two letters, sealed together, opening at the same moment wherever you both are by then.
Both write before one checkout. The year begins only when payment is verified and both letters are written. Keep them private, or agree to an exchange: on the opening date, you read theirs and they read yours. Either person can call the exchange off before then. Keep the private key links safe; the service handles keys transiently for email and ownership checks.
Encrypted in your browser. Scheduled to open one year after verified sealing; pairs need verified payment and both letters written first. Keep your private key link safe. US$5 for one letter, US$9 for two.