What little is known about St. Tib has likely been made up entirely.
Luckily, there is some debate about how this day is to be scheduled. There are even dueling popes!
Though the Principia Discordia says that the day occurs once every 4 years, it first says that the Discordian and Gregorian calendars are perpetually aligned. Thus, we can reason that we actually only insert St. Tib's Day into every 4th year that does not end in 66, unless that year's century is 3 more than a multiple of 4. For example, 3166 does contain a St. Tib's Day, but 3066 didn't and 3266 won't.
And from Pope Jess Cully comes a differing point of view
The Discordian Calendar will thus diverge from the Gregorian on St. Tib's Day 3266 (March 1, 2100 Gregorian). From 3267 to 3366, the Discordian year will begin on January 2 Gregorian. Those who wish to express the relationship between the Discordian and Roman Calendars in an invariable way may do so thus : The Discordian year begins on December 19 according to the Julian Calendar.
A Gregorian parallel maintains five quite nicely. Diverging from this, however, will maintain five quite nicely.
Tell everyone today is your birthday. Figure out how old you would be if you only had a birthday once every leap year. Act your age. Determine if you're of legal age to drive, raise children, buy a gun, gamble, leave school, get a job, drink, get married, get drafted, sign a contract, vote, run for parliament or congress, have sexual congress, have sexual congress for money, retire, or walk across the street by yourself. Realize how silly having a legal age for everything really is, and how arbitrary it is, and how it doesn't recognize the individual as an individual, and how it's all culturally-biased ageism anyway. Forget about age limits, and do whatever you want. If you're lucky, maybe you can convince them you're too young to get arrested for doing any of the above (but don't count on it).