The countdown runs in your browser: the date is not sent or kept anywhere. Someone born on 29 February is counted on 1 March in the years without one.
How the countdown works
It takes today's date and the next anniversary of the date of birth. If the birthday has already passed this year, it counts to next year's. The age shown is the one they will turn on that day, and the number of days lived is counted from the date of birth to today.
Do not miss it
When the countdown gets short, a card with a game in it takes about a minute to make: their name and age are written into the game, and it is sent as a link on WhatsApp, by text or by email. Ideas by person and by age are on the birthday messages page, and every card is on birthday cards.