May 31, 2026, is the 151st and final day of May, with 214 days remaining in the year, and it falls on a Sunday — the last Sunday of the month — in the twenty-first week of the year.
With 15 national and international days on the calendar, May 31 closes out the month with genuine weight: World No Tobacco Day has been the WHO’s flagship health observance on this date since 1987, Trinity Sunday brings the Easter liturgical season to its theological conclusion, and World Foster Day advocates for hundreds of thousands of children in care. The day also asks you to smile at a stranger, speak in complete sentences, protect your hearing, appreciate a web designer, and consider what you’ve been thinking about — because apparently it grows.
National Days on May 31
All national & international days celebrated today
15 celebrations on this dayWorld No Tobacco Day
Established by the WHO in 1987 and observed every May 31, World No Tobacco Day draws global attention to the tobacco epidemic — the leading cause of preventable death worldwide, killing over 8 million people annually, with 1.2 million of those deaths from secondhand smoke. Each year the campaign focuses on a specific theme, from plain packaging to tobacco industry interference.
Trinity Sunday
The first Sunday after Pentecost in the Western Christian liturgical calendar, Trinity Sunday celebrates the Christian doctrine of the Holy Trinity — the Father, the Son, and the Holy Spirit as three Persons of one God. It is one of the few feast days in the Church year that honours a doctrine rather than an event or person, and falls on May 31, 2026 — one week after Pentecost.
World Foster Day
World Foster Day raises awareness of the global foster care system and the children, foster carers, and birth families within it. Around the world, millions of children live in foster care — and the day highlights both the need for more foster families and the importance of supporting those already providing care. In the US alone, over 400,000 children are in the foster care system at any given time.
World Parrot Day
Established by the World Parrot Trust, World Parrot Day on May 31 raises awareness of wild parrot species threatened by the illegal pet trade and habitat destruction. Parrots are among the most intelligent birds on Earth — capable of learning hundreds of words, solving complex puzzles, and forming deep social bonds — yet over a third of the world’s 400 parrot species are threatened with extinction.
Here’s every observance celebrated on May 31, 2026.
National & International Days on May 31
Whether you’re marking World No Tobacco Day, attending a Trinity Sunday service, advocating for children in foster care, protecting wild parrots, smiling at someone, speaking very completely and grammatically, or simply finishing May on a thoughtful note, here’s the story behind each of these May 31 celebrations.
Infidelity Hurts Awareness Day
Infidelity Hurts Awareness Day was founded by Christina Renee, a member of the American Psychological Association, as a way to give voice to those affected by infidelity. She created the day to provide a safe and honest space for people to process their experiences without shame. Originally called Infidelity Speaks Awareness Day, the observance highlights the emotional damage caused by betrayal and challenges how infidelity is often downplayed in culture and relationships.
International Flight Attendant Day
International Flight Attendant Day, sometimes also called International Cabin Crew Day, honors the dedication and professionalism of flight attendants worldwide. Celebrated on May 31 since at least 2015, the day recognizes the crucial role these crew members play in passenger safety, comfort, and travel experience. It’s an opportunity to thank the people who guide us through takeoff, turbulence, and touchdown with care and calm.
National Autonomous Vehicle Day
National Autonomous Vehicle Day brings attention to the evolving world of self-driving technology. Celebrated since 2017, the day was founded by Emerging Prairie and Marlo Anderson to spotlight innovation in autonomous transport—from cars to drones. It marks a turning point in how we think about travel, commerce, and the future of mobility.
Necrotizing Fasciitis Awareness Day
Necrotizing Fasciitis Awareness Day raises awareness about a rare but serious bacterial infection that can spread quickly through the body’s soft tissue. Often called a “flesh-eating disease,” necrotizing fasciitis requires early diagnosis and urgent treatment to prevent severe complications. This day has been observed annually on May 31 since 2017 to support education, prevention, and early intervention.
National Macaroon Day
National Macaroon Day celebrates the small, chewy coconut cookie that’s often mistaken for its French cousin, the macaron. Traditionally made with almonds, egg whites, and sugar, the macaroon has been a Passover staple and a favorite treat for centuries. Its roots trace back to an 8th-century French monastery, and the cookie gained popularity thanks to two nuns in Nancy during the French Revolution. Over time, coconut became the signature ingredient in American-style macaroons.
National Save Your Hearing Day
National Save Your Hearing Day reminds us to take care of one of our most important senses. Observed every year on May 31, the day promotes awareness about noise-induced hearing loss and encourages protective habits, like using earplugs or turning down the volume. The goal is to prevent avoidable damage and preserve hearing throughout life.
National Smile Day
National Smile Day was established in 2018 by Dr. Tim Stirneman and Jim Wojdyla of Compassionate Dentalcare. Their goal was to highlight the power of a healthy smile to boost confidence and improve quality of life. The day encourages everyone to share a smile and acknowledge the emotional and physical benefits it brings.
National Speak in Complete Sentences Day
National Speak in Complete Sentences Day celebrates the structure and clarity of language. Held annually on May 31, the day challenges people to use proper grammar and full sentences in everyday speech and digital communication. It’s a fun way to improve language skills while appreciating the importance of effective communication.
National Utah Day
National Utah Day honors the 45th state to join the Union—Utah, admitted on January 4, 1896. Known as the Beehive State, Utah is celebrated for its stunning desert landscapes, Native American heritage, and unique geological landmarks like Arches National Park and the Bonneville Salt Flats. National Utah Day invites people to learn more about the region’s cultural history, natural beauty, and contributions to science and recreation.
What You Think Upon Grows Day
What You Think Upon Grows Day was created in 2002 by Stephanie West Allen, a lawyer and writer who wanted to promote the power of positive thinking. The observance falls on May 31 in honor of Norman Vincent Peale, a pioneer of the modern positive thinking movement. The day encourages focusing on thoughts that foster growth, gratitude, and mental well-being.
Web Designer Day
Web Designer Day recognizes the creative professionals who build and shape our digital experiences. While its exact origins are unclear, the day acknowledges how far web design has come—from simple HTML pages to today’s interactive, user-centered websites. It’s a chance to thank the designers behind the screens for improving online functionality and aesthetics.
World Foster Day
World Foster Day started in 2018 to raise awareness about the importance of foster care and to celebrate families who open their homes to children in need. Organized as part of broader campaigns like National Foster Care Month and Foster Care Fortnight, the day aims to educate communities and encourage greater support for vulnerable children across the globe.
World No Tobacco Day is a global health observance that highlights the harms of tobacco use and promotes policies to reduce smoking worldwide. Coordinated by the World Health Organization since 1987 and observed in more than 190 countries, it exists alongside Cigarettes Are Hazardous to Your Health Day on January 11, which focuses on the United States and commemorates the 1964 U.S. Surgeon General’s report that first confirmed smoking causes serious disease and launched modern anti-smoking efforts.
World Parrot Day
World Parrot Day was launched in 2004 by the World Parrot Trust to spotlight the challenges parrots face in the wild and in captivity. The inaugural event included a rally in London’s Trafalgar Square and a petition to ban wild parrot imports to the European Union. The day promotes conservation efforts and celebrates the intelligence and diversity of these colorful birds—especially species like the African grey parrot, known for remarkable cognitive abilities.
