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Atheist Day

An annual observance on March 23 recognizing atheism and promoting awareness of secular perspectives, religious freedom, and the separation of church and state.

Tuesday

March 2027

Last updated March 18, 2026 · by the Holiday Calendar Team

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YEARLY DATEMarch 23

OBSERVED INUnited States

CATEGORYAwareness

SUBCATEGORYValues

ORIGIN

Community Origin

FOUNDING ENTITY

Spanish Union of Atheists and Freethinkers

FIRST OBSERVED

2009

HOW THE HOLIDAY CAME TO BE

The Spanish Union of Atheists and Freethinkers first celebrated Atheist Day on March 23 in 2009. Multiple international organizations, including Atheist Republic and the International Coalition of Ex-Muslims, subsequently adopted the date. A satirical internet story from 2003 had previously placed the observance on April 1; the March 23 date was chosen to separate it from that mockery.

INTRO

Introduction

PHOTO

Atheist Day exists in part because of an internet joke. In 2003, a satirical story went viral claiming a judge had told an atheist plaintiff that April Fools' Day was already their holiday. The story was fictional, but it stuck. When secular organizations formalized the observance in 2009, they deliberately chose March 23 to distance it from the punchline.

The holiday now serves a more substantive purpose. The share of Americans identifying as atheist has doubled since 2007, and the broader category of religiously unaffiliated adults has reached 28% of the population. Atheist Day marks a demographic shift that is reshaping American civic life.

ORIGINS

Atheist Day history

INTRODUCTION

Atheism in America did not start in the 21st century. The period from 1860 to 1900 is known as the Golden Age of Freethought, when public intellectuals openly questioned religious authority and traveled a national lecture circuit that drew large audiences. The movement had enough momentum that by 1925, the American Association for the Advancement of Atheism became one of the country's first formal organizations dedicated to nonbelief.

The American Humanist Association followed in 1941, broadening the secular movement beyond atheism into a philosophical framework that emphasized ethics without religion. These organizations laid the groundwork, but atheism remained largely invisible in mainstream American life. That changed with one person.

CHAPTER 01

The most hated woman in America

Madalyn Murray O'Hair was a Baltimore mother who challenged the practice of mandatory Bible reading in her son's public school. Her case, Murray v. Curlett, reached the Supreme Court in 1963, where it was consolidated with Abington School District v. Schempp. The Court ruled that officially mandated Bible reading in public schools was unconstitutional.

That same year, O'Hair founded American Atheists. In 1964, Life magazine called her "the most hated woman in America." She was confrontational, litigious, and unapologetic. She pursued cases to remove "In God We Trust" from currency and to revoke tax exemptions for churches. She remained the public face of American atheism until her death in 1995.

CHAPTER 02

From internet joke to formal observance

In 2003, a satirical internet story claimed a judge had told an atheist plaintiff that April Fools' Day was already their holiday, citing the biblical verse "The fool says in his heart, 'There is no God.'" The story was entirely fictional, but it spread widely enough to permanently link atheism with April 1 in popular culture.

When the Spanish Union of Atheists and Freethinkers organized the first formal Atheist Day in 2009, they chose March 23 specifically to break that association. The date gave the observance its own identity, separate from any punchline. Organizations including Atheist Republic and the International Coalition of Ex-Muslims subsequently adopted it, turning March 23 into a global day of visibility for nonbelievers.

TIMELINE

Atheist Day Timeline

First atheist advocacy group founded

The American Association for the Advancement of Atheism was established, becoming one of the earliest formal organizations in the United States dedicated to promoting atheism and the separation of church and state.

Supreme Court bans mandatory school prayer

The Supreme Court ruled in Abington School District v. Schempp, consolidated with Murray v. Curlett, that mandatory Bible reading and prayer in public schools was unconstitutional. The case was brought by Madalyn Murray O'Hair, who that same year founded American Atheists.

Satirical Atheist Day story goes viral

A fictional internet story claimed a judge told an atheist that April Fools' Day was already their holiday, citing a biblical verse about fools. The story was widely shared as fact and linked atheism with April 1 in popular culture.

First formal Atheist Day observed

The Spanish Union of Atheists and Freethinkers organized the first official Atheist Day on March 23. The date was chosen to separate the observance from the April 1 satirical association and establish it as a day of genuine advocacy.

Atheists reach 4% of U.S. adults

Pew Research Center data showed that 4% of American adults identified as atheist, up from 2% in 2007. The broader category of religiously unaffiliated Americans, including atheists, agnostics, and those claiming no religion, reached 28% of the adult population.

GET INVOLVED

How to Celebrate Atheist Day

Read the Supreme Court decision

The full text of Abington School District v. Schempp is available online. The 1963 ruling redefined the relationship between religion and public education in the United States and remains one of the most cited First Amendment cases.

LEARN

Learn about the demographics of nonbelief

Explore Pew Research Center's data on religious demographics in America. The numbers reveal how rapidly the religious landscape is changing and how atheism intersects with age, education, geography, and politics.

WATCH

Watch a debate or lecture

Find recorded public debates between theists and atheists, or watch lectures from prominent secular thinkers. The intellectual tradition of public argumentation about religion is centuries old and remains one of the most substantive forms of civic discourse.

SUPPORT

Support a secular organization

Organizations like the Freedom From Religion Foundation and American Atheists work on church-state separation cases and provide legal support for nonbelievers. Atheist Day is an opportunity to learn about their work.

HAVE

Have an honest conversation

If you are comfortable doing so, talk to someone about what you believe and why. Atheist Day is designed to normalize open discussion about nonbelief, not to convert anyone but to make the conversation itself less unusual.

WHY THIS DAY MATTERS

Why Atheist Day is Important

It connects to a global movement for freedom of belief

Atheist Day is observed internationally, with particular significance in countries where apostasy carries criminal penalties. The International Coalition of Ex-Muslims uses March 23 to show solidarity with atheists who face persecution for leaving religion. The observance links American secular advocacy with a global human rights issue.

The nonreligious population is growing faster than any faith group

Pew Research data shows that religiously unaffiliated Americans, the 'nones,' grew from under 10% in the 1990s to 28% in 2023. Within that group, self-identified atheists doubled from 2% to 4% between 2007 and 2023. Approximately two-thirds of nones are former believers. Atheist Day marks a demographic trend that is accelerating.

It addresses ongoing legal and social challenges

Despite constitutional protections, atheists in the United States face social stigma and, in some states, outdated laws that technically bar nonbelievers from holding public office. Seven state constitutions still contain religious test provisions, even though they are unenforceable under the federal Constitution. Atheist Day draws attention to the gap between legal rights and social acceptance.

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