One link. Your friends read themselves onto it.

Share one link and the people who open it add themselves — their own birth date, their own consent, on their own screen. Nobody gets added by somebody else.

The result is a map rather than a list: you can see how a group's days sit together, which weeks suit everyone and which suit nobody. It is explicitly not a ranking of your friends, and it says so on the screen.

You can delete a map at any time. Doing so removes it for everyone on it.