Now in its sixth year, Pi Day Princeton celebrates the birthday of the most famous scientist ever to call Princeton home, the mathematical constant pi, and the happy coincidence that Albert Einstein’s birthday, March 14, is the numerical equivalent of pi (3.14). This year’s 135th birthday party of Einstein spans from Thursday to Saturday, March 13 to 15.

The brainchild of Princeton Tour Company founder Mimi Omiecinski, Pi Day has only grown since the inaugural event in 2009 and includes numerous local merchants as well as the Princeton Public Library and the Historical Society of Princeton.

In addition to a wide array of pi- and pie-themed events for all ages (see listings below), merchants join in the fun by offering pi-themed discounts including restaurant items and theater tickets priced at $3.14. A free smartphone tour about Eintsein and Princeton will be released at 3:14 p.m. on Friday, March 14.

Thursday, March 13

7 p.m.: Physics professor and author Charles Adler presents “Wizards, Aliens, and Starships: Physics and Math in Fantasy and Science Fiction.” Adler, a faculty member at St. Mary’s College of Maryland, discusses technologies from science fiction and fantasy literature that could exist in real life. Princeton Public Library.

Friday, March 14

11 a.m.: Walking tour of Einstein’s neighborhood. Princeton U-Store, 116 Nassau Street.

3:14 p.m.: Walk a Pi (3.14 miles) event. YMCA Princeton, 59 Paul Robeson Place.

3:14 p.m.: Pizza Pi Competition for grades 6-8. Register to princetonmimi@gmail.com or in store. Princeton Pi, 86 Nassau Street.

6 p.m.: Academic Celebrity Pi Day Event with Yale physics professor A. Douglas Stone presenting “Einstein and the Quantum: The Quest of the Valiant Swabian.” Stone is a professor of applied physics and physics at Yale University. Princeton Public Library.

8 p.m.: Princeton Light Up the Night Event: A recreation the 1,000 fireflies experiment. The first 159 Princeton residents to arrive will receive LED lights for their bikes and ride 3.14 miles on the circular track. The lights will synchronize to create an artificial system of blinking lights. Register to princetonmimi@gmail.com. Community Park South.

Saturday, March 15

9 a.m.: Pie Eating Contest. McCaffrey’s, Princeton Shopping Center.

10 a.m.: Princeton Symphony Orchestra holds a violin exhibition for ages 3 to 6. For more information E-mail cburden@princetonsymphony.com. Princeton Public Library Community Room.

11 a.m. and 4 p.m.: Happy Birthday Party, Albert! For ages 6 to 12. $5 per child. Register at 609-921-6748, ext. 102 or eve@princetonhistory.org. Historical Society of Princeton, 158 Nassau Street.

11 a.m.: Einstein Look-Alike Contest. Register to princetonmimi@gmail.com. Princeton Public Library Community Room.

Noon: Dinky train rides with Einstein. Departing Princeton Station at noon, 12:27 p.m. and 1 p.m.; departing Princeton Junction Station at 12:11 p.m., 12:37 p.m. and 1:11 p.m. $2.75 per adult each way, up to two kids (ages 5-11) can ride free with a passenger paying any valid fare. Dinky and Princeton Junction Train Stations.

Noon to 12:45 p.m.: Tetsuya Miyamoto, inventor of KENKEN, the popular number puzzle. A math teacher in Japan, Miyamoto invented the puzzle for his students. Its Japanese name literally means “a puzzle that makes you smarter.”

In each puzzle, a square grid must be filled with numbers (e.g., 1 through 5 for a 5x5 grid) in such that no number is repeated in any row or column. In addition, areas of the grid specify numbers and the basic operation used to find it. For example, adjacent squares might be labeled “3+” indicating that the numbers in the two squares must add up to three. Princeton Public Library Community Room.

1 to 2 p.m.: KENKEN Tournament for teens (and other teen-spirited humans). Princeton Public Library third floor teen area.

Noon to 2 p.m.: Author Jennifer Berne of “On a Beam of Light — A Story of Albert Einstein” reads and signs books. Berne studied art and eventually became an advertising copy writer — all the while nourishing a life-long interest in science and the universe. Those interests became the topics for her children’s books. “On a Beam of Light” tells the true story of a curious little boy named Albert Einstein. Jazam’s, 25 Palmer Square East.

1 p.m.: Pi Recitation Contest. For ages 13 and under. Register to princetonmimi@gmail.com. Princeton Public Library Community Room.

1:30 to 2 p.m.: Finding Pi: calculate pi for yourself with two hands-on activities. For ages 5 and up. Princeton Public Library Lobby.

2 p.m.: Bedtime Math Book Party & Activities with Laura Overdeck. Bedtime Math is a nonprofit that offers daily math problems and math books to help kids learn to love math. Overdeck, who earned her bachelor’s degree in astrophysics from Princeton, started the program with her husband after giving her own kids light-hearted math problems and hearing them beg for more. Labyrinth Books, 122 Nassau Street.

2:15 p.m.: Princeton University Rubik’s Cube Club demonstrates how to solve a Rubik’s Cube. Princeton Public Library.

2:45 p.m.: Pie Judging Contest. Yankee Doodle Tap Room, Nassau Inn.

3:14 p.m.: Pie Throwing Event. $1 per throw benefits 101: A non profit organization dedicated to helping Princeton High School graduates in need of financial assistance. Palmer Square Green.

3:30 p.m.: Guided Einstein Tour by Mimi Omiecinski, founder of Pi Day Princeton and owner of Princeton Tour Company and Princeton Genius Tours. Princeton Public Library Lobby.

5 p.m.: Pi Social featuring PiFight, the Einstein Alley Rock and Roll Band. Princeton Public Library Community Room.

7:30 p.m.: The Princeton Theatre Experiment in collaboration with the Arts Council of Princeton will present an Einstein-themed original dramatic production. Arts Council of Princeton.

For more information visit www.pidayprinceton.com.