A person born on February 29 may be called a "leapling". In common years they usually celebrate their birthdays on 28 February or 1 March.
For legal purposes, their legal birthdays depend on how different laws count time intervals. In Taiwan, for example, the legal birthday of a leapling is 28 February in common years, so a Taiwanese leapling born on February 29, 1980 would have legally reached 18 years old on February 28, 1998.
In some situations, March 1 is used as the birthday in a non-leap year since it then is the day just after February 28.
There are many instances in children's literature where a person's claim to be only a quarter of their actual age turns out to be based on counting only their leap-year birthdays. A similar device is used in the plot of the Gilbert and Sullivan operetta The Pirates of Penzance.