Holiday Calendar

National Smile Day

Next celebratedMonday, May 31, 2027

The muscle that rings the eye in a real smile cannot be fired on command, which is why a posed one looks hollow. The day borrows that face for a dental-care push aimed at the fear that keeps people out of the chair.

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Last updated September 5, 2026 · by the Holiday Calendar TeamHave an update or spot an error?
YEARLY DATEMay 31
OBSERVED INUnited States
CATEGORYHealth
SUBCATEGORYSelf-Care
ORIGIN

Corporate Initiative

FOUNDING ENTITY
Compassionate Dental Care (Dr. Tim Stirneman and Jim Wojdyla)
FIRST OBSERVED
2019
“Two men at one Illinois dental office created May 31 as National Smile Day, and the whole of May as National Dental Care Month.
HOW THE HOLIDAY CAME TO BE

A dental office's marketing idea, stated plainly.

Dr. Tim Stirneman and Jim Wojdyla of Compassionate Dental Care in Lake in the Hills, Illinois founded National Smile Day for May 31, alongside National Dental Care Month for the whole of May, and announced both in a press release dated April 30, 2019. Their 2018 children’s book had already placed a girl’s first dental visit on that date.

Read the founders' announcementvia Compassionate Dental Care
INTRO

The dental office that built itself a holiday

Most holidays hide their commercial roots. National Smile Day prints them on the box. The two men who created it, a dentist and his business-development partner at a single office outside Chicago, said in their own announcement that the day was "created for marketing campaigns and social media content creation."

That candor is rarer than the day itself. May 31 has no act of Congress behind it and no ancient custom, only a working dental practice that wanted a reason for offices like its own to talk about teeth.

What sits underneath the marketing, though, is real. The smile is one of the most studied expressions in science, traced muscle by muscle since the 1860s, and roughly 1 in 4 American adults walk around with untreated tooth decay, the exact gap the day points at.

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ORIGINS

Smile Day history

INTRODUCTION

Long before any dentist filed for a holiday, the smile was a problem for scientists. It looked simple and behaved strangely. People could fake one, yet a fake rarely fooled anyone, and nobody could quite say why.

The first person to take the question apart was a French physician. In the 1860s, Guillaume Duchenne de Boulogne ran small electrical currents through the faces of his subjects, firing one muscle at a time. His 1862 book, Mecanisme de la Physionomie Humaine, isolated the two muscles a real smile uses.

CHAPTER 01

The muscle that gives you away

One muscle pulls the corners of the mouth up. The other rings the eye and crinkles its outer skin. Duchenne noticed the mouth muscle obeys the will, but the eye muscle does not.

He argued it was moved only by genuine feeling, which is why a posed smile so often looks hollow. A century later, that distinction became the textbook test for a sincere smile.

CHAPTER 02

From a Paris lab to a calendar

Charles Darwin picked up the thread in 1872, proposing that an expression can feed the emotion behind it. The idea drew researchers for the next 150 years.

None of them, however, set a date for it. That fell to Dr. Tim Stirneman, who runs Compassionate Dental Care in Lake in the Hills, Illinois, and his director of business development, Jim Wojdyla.

Stirneman counted close to 70 dental offices within six miles of his own. Rather than fight them for patients, he pitched a shared cause: a day, and a whole month, that any practice could rally around. So the pair registered May 31 as National Smile Day and the whole of May as National Dental Care Month.

CHAPTER 03

A children's book hid the date

They were not subtle about the through-line. In 2018 the two co-wrote and illustrated a children's book, Mya Papaya Meets the Wizard of Teeth, about a girl's first trip to the dentist. The day of her appointment in the story is May 31, the same date they had claimed for the holiday.

WHY THIS DAY MATTERS

Why We Love National Smile Day

FEAR

Most people avoid the dentist out of fear, not forgetfulness.

A 2025 nationally representative survey found that 72.6 percent of US adults report some fear of the dentist, with 26.8 percent calling it severe. A cheerful, low-stakes day is the trade's attempt to make the chair feel approachable rather than scolding people into it.

ACCESS

Routine care is the whole point

Nearly 90 percent of US adults ages 20 to 64 have had tooth decay at some point, much of it preventable with regular visits. The day's dental-awareness framing is a nudge toward the cleanings and checkups that catch problems early.

SCIENCE

The smile is a genuine object of study

The expression has been mapped muscle by muscle since 1862 and remains a live subject in psychology and anthropology. The day gives a centuries-old research thread a spot on the popular calendar.

BY THE NUMBERS

National Smile Day by the Numbers

~1 in 4
US adults 20-64 with untreated decay
~90%
US adults 20-64 who have had decay
72.6%
US adults reporting dental fear (2025)
1862
Year Duchenne mapped the genuine smile

TIMELINE

Timeline

Duchenne maps the genuine smile

French physician Guillaume Duchenne published Mecanisme de la Physionomie Humaine, isolating the two muscles a sincere smile uses.

Darwin links face and feeling

Charles Darwin argued that expressing an emotion can intensify it, an early version of the facial-feedback idea.

A coding system revives the work

Paul Ekman and Wallace Friesen built the Facial Action Coding System, reviving Duchenne's marker for a genuine smile.

A famous smile study fails to replicate

Seventeen labs together could not reproduce the classic 1988 experiment that claimed forcing a smile makes things funnier.

A children's book sets the date

Stirneman and Wojdyla published Mya Papaya Meets the Wizard of Teeth, in which the girl's first dental visit falls on May 31.

A dental office founds the day

A press release dated April 30, 2019 announced National Smile Day for May 31 and National Dental Care Month for all of May.

GOOD TO KNOW

Surprising facts about National Smile Day

The smile may have started as a threat

Researchers widely trace the human smile to a primate "silent bared-teeth display," a nervous show of teeth that subordinates give to dominant group members. The friendly meaning came later.

Smiling and laughing may not be relatives

Some scientists argue the smile and the laugh have separate evolutionary roots: the smile from the bared-teeth display, the laugh from a relaxed, open-mouthed "play face."

Duchenne's research sat unused for a century

His muscle-by-muscle work was largely ignored until the 1970s, when Ekman and Friesen revived it to build a system that catalogs thousands of facial movements.

The same founders claimed an entire month too

Alongside May 31, Stirneman and Wojdyla registered the whole of May as National Dental Care Month, framed around the line that dentistry is cheaper than neglect.

The one point that we always stress is that dentistry isn't nearly as expensive as neglect is.
Jim WojdylaDirector of Business Development, Compassionate Dental Care

MYTH VS FACT

Common Misconceptions

The myth

Science has proven that forcing a smile reliably makes you happier.

The truth

The famous 1988 "pen in the teeth" experiment that suggested this failed a 17-lab replication in 2016, which found essentially no effect. The broader idea is still debated, not settled.

The myth

People with bigger smiles in photos are proven to live longer.

The truth

A 2010 study of baseball cards suggested this, but a 2018 re-analysis found the effect vanished once players' birth years were accounted for, pointing to a false positive.

The myth

National Smile Day and World Smile Day are the same holiday.

The truth

They are separate. World Smile Day falls on the first Friday in October and was created in 1999 by Harvey Ball, who drew the original 1963 smiley face. National Smile Day is the US dental observance on May 31.

GET INVOLVED

How to Celebrate National Smile Day

EDITOR'S PICK

Book the dental visit you have been avoiding

The day exists to nudge exactly this. Use it as the prompt to schedule the cleaning or checkup that has slipped down your list, especially if it has been more than a year.

LEARN

Learn what makes a smile look genuine

A real smile crinkles the skin around the eyes, the part Duchenne found you cannot fake on command. Watch for it in photos of yourself and others and you will start to see the difference.

READ

Read up on the science before you share it

Plenty of popular smile facts did not survive replication. Check the claim against a source like the Association for Psychological Science before you pass it along.

HELP

Help someone clear a dental-care barrier

Cost and fear keep many people out of the chair. Offer to drive a nervous friend to an appointment, or support a local free-care clinic that treats people without insurance.

GIVE

Give a real reason to smile

Send one specific, honest compliment to someone who would not expect it. It costs nothing and does more for the spirit of the day than any post about it.

Test your knowledge

How well do you know National Smile Day?

1 / 8

Who created National Smile Day?

Answer

It is observed every year on May 31 in the United States.

COLOPHON

Sources

How we know what’s on this page. References, not endorsements.

9sources
6primary records
7independently dated
Primary records
Compassionate Dental Care2019-04-30
Local Dentist Office Founders of Two New National Holidays
The founders' own announcement of National Smile Day and National Dental Care Month, with their stated marketing purpose.
View source
World Smile Foundation
About Harvey Ball
How Harvey Ball drew the 1963 smiley face and created the separate World Smile Day in 1999.
View source
National Institute of Dental and Craniofacial Research2011-2016
Dental Caries (Tooth Decay) in Adults (Ages 20 to 64 Years)
Federal survey data showing about 1 in 4 adults have untreated decay and nearly 90 percent have had it.
View source
NIH National Library of Medicine2021
A Novel Test of the Duchenne Marker
Background on Duchenne's 1862 electrical-stimulation work and the modern marker for a genuine smile.
View source
Frontiers in Psychology2021
Complexity and Phylogenetic Continuity of Laughter and Smiles in Hominids
Research on the smile's roots in a primate bared-teeth display and the separate origin of laughter.
View source
Psychological Science2018
Does Smile Intensity in Photographs Really Predict Longevity?
A 2018 re-analysis finding the smile-and-longevity link disappears once birth year is controlled.
View source
Additional coverage
American Dental Association2025-09
September JADA finds dental fear still prevalent in US
A 2025 nationally representative survey finding 72.6 percent of US adults report fear of the dentist.
View source
Association for Psychological Science
The Psychological Study of Smiling
Explains the two muscles of a true smile and how Ekman and Friesen revived Duchenne's work.
View source
ScienceDaily2016-10
Smile, you'll feel better? A 17-lab replication
Reports the 2016 multi-lab effort that failed to reproduce the classic facial-feedback experiment.
View source
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