It can be a leap in the dark for those who want to wish Ms Alia Zulkifli happy birthday.
They are told on Facebook on Feb 28 that the birthday of the Singapore Institute of Technology student is the next day, but the notice disappears on March 1.
"I get the occasional 'I don't know which day to wish you!' from my friends on non-leap years, which I find quite funny," she said.
This being a leap year, her friends likely had no problem sending birthday greetings to Ms Alia, who turned 24 yesterday - Feb 29.
For "leaplings", as those who are born on Feb 29 are called, having fewer birthdays is just one of the unusual and sometimes annoying situations that they find themselves in.
Feb 29 occurs once every four years on the 365-day Gregorian calendar. As it takes 365.24 days for the Earth to completely orbit the Sun, a day is added to a leap year to catch up with the solar year.
Singapore Management University undergraduate Norman Yam, who also turned 24 yesterday, said some people think it is a joke when he says he was born on Feb 29.
"Most of the time nobody believes that it's my real birthday. I often have to show my ID," he said.
He also cannot register his birth date sometimes when creating accounts online. "On some websites, when that happens, I put my birthday as Feb 28 instead," he added.
Civil servant Teanna Tan, 24, has six candles on her cake and misses gifts that others take for granted.
"Places like the zoo, for instance, give free entry every year on birthdays, but I never ever get it. I have the chance to enjoy birthday privileges only once every four years, so that's not fun," she said.
The chance of someone being born on Feb 29 is one in 1,461, which means there are about 3,700 leap-year babies among Singapore's population of 5.54 million.
One of them, the second child of sales manager Goo Kim Liong, 39, was born in Mount Alvernia Hospital yesterday. Said Mr Goo: "The boy was supposed to be due in March, but he chose to come out on Feb 29 - and exactly at midnight, so it's so much more special."
But being born on Feb 29 does not have to mean fewer birthday parties. He said: "I guess we can still celebrate his birthday every year according to the Chinese calendar, so that's fine. Maybe every four years, we will have a grand celebration."
Some leapt at the chance to register their marriages on the unique day, like Mr Tan Qing Lin, 34, and Ms Valerie Sim, 26.
"I waited by my computer at midnight when this date became available for registration three months ago. I was afraid that the date would be very popular with other couples," said Mr Tan, a technical research coordinator.
Ms Alia likes her unique birthday. "There's actually a Facebook group dedicated to 'leaplings' from around the world and we all share the same problems."