For Siblings Day, lion cubs wrestle in Samburu National Park, Kenya (© Mark C. Ross/Getty Images)

Books by Hans Christian Andersen (© radiokafka/Adobe Stock)

Milky way over the Bisti/De-Na-Zin Wilderness in New Mexico, USA (© Cory Marshall/Tandem Stills + Motion)

For Earth Month, a symmetrical forest known as a Nelder Plot (© Rachid Dahnoun/Tandem Stills + Motion)

Blossoming cherry trees at a tea plantation in Longyan, China (© VCG/Getty Images)

Garlands of red and yellow flowers, on Ugadi (© Sviridenko/iStock/Getty Images Plus)

For International Beaver Day a beaver swimming in Grand Teton National Park (© Charlie Hamilton James/Getty Images)

Auroville, South India (© Vikram Ramakrishnan/Shutterstock)

Bioluminescent algae along the shores of the Matsu Islands off the coast of Taiwan (© Wan Ru Chen/Getty Images)

Dutch tulip fields in the Duin- en Bollenstreek region for the Amsterdam Tulip Festival (© Frans Sellies/Getty Images)

The Mount Washington Observatory in New Hampshire, USA (© Mike Theiss/Getty Images)

Vinyl records in Rosmalen, The Netherlands (© DutchScenery/Shutterstock)

Dr. Bhimrao Ambedkar Samajik Parivartan Prateek Sthal (© gitika n manas/Shutterstock)

A woman looks at Yayoi Kusama's 'With All My Love for The Tulips, I Pray Forever (2011)' (© Timothy A. Clary/Getty Images)

Bauhaus Archive Museum of Design in Berlin, Germany (© Juergen Henkelmann Photography/Alamy)

Hope Valley, Peak District, England (© Daniel_Kay/Getty Images Plus)

Dubai Miracle Garden, United Arab Emirates (© Amazing Aerial/Offset)

Paepalanthus flowers at sunset, Chapada dos Veadeiros National Park, Brazil (© Marcio Cabral/Getty Images)

The Cove of Spires in Kenai Fjords National Park near Seward, Alaska, USA (© Grant Ordelheide/Tandem Stills + Motion)

A rabbit in the grass (© wisan224/Getty Images Plus)

Laysan albatross chick on Midway Atoll, Hawaiian Leeward Islands (© Jaymi Heimbuch/Minden Pictures)

At Casa Batlló for Saint Jordi’s Day in Barcelona, Spain (© Jon Arnold Images Ltd/Alamy)

Paragliding in Kamshet and Panchgani, Maharashtra. (© Deep Pai/Moment/Getty Images)

Ice cave at sunset in Vatnajokull, Iceland (© Johnathan Ampersand Esper/Aurora Photos)

Coast redwoods in Henry Cowell Redwoods State Park, California (© Gallery Stock)

Hummingbird near blooming aloe vera in Laguna Beach, California, USA (© Aurora Photos/Offset)

Eagle owl bird of prey in Karnataka. (© Anantha Murthy H S/iStock/Getty Images Plus)

Newborn brown-throated sloth with mother, Sloth Sanctuary of Costa Rica (© Suzi Eszterhas/Minden Pictures)

Louis Armstrong performs with bandmates in Vienna, Austria, on February 22, 1959 (© Franz Hubmann/Getty Images)

Wisteria blooms at Kawachi Fuji Gardens in Kitakyushu, Japan (© Wibowo Rusli/Alamy)