It is supported by Jude Law (pictured) and in previous years has been backed by Angelina Jolie, Annie Lennox and Lenny Kravitz. But international non-profit organisation Peace One Day now wants UK primary school children (aged 5-11) to get involved, writing a Poem for Peace and engaging in a global day of peace.
The theme for this year's Peace Day on 21 September is "Who will you make peace with?" And the school poetry competition, launched this month, is designed to get children to use their imaginations and to encourage the creative use of language to improve literacy.
Ask children what springs to mind when they think about peace. What colour is it? What objects and scenes do they associate with it? Which words?
A video and lesson plan to help children write a Poem for Peace are available as part of Peace One Day's primary education resources. Poems can be up to 12 lines long and must be submitted by 18 August. The winner will receive a prize that includes four tickets to the Peace One Day celebration on 21 September at the Peace Palace in The Hague, Netherlands. The poem should incorporate at least two key devices of poetry - for example, rhyming, metaphor and alliteration - and focus on Peace Day.
Peace One Day was founded in 1999 by Jeremy Gilley, an actor turned film-maker who, in the late 1990s, became preoccupied with questions of peace and humanity's survival.
In 2001, a resolution was unanimously adopted by United Nations member states, formally establishing Peace Day as an annual day of global ceasefire and non-violence.
An estimated 280 million people were aware of the day in 2012. Peace One Day aims to reach 3 billion people by 2016 and has launched free, online education resources to drive debate and practical action among students.
This year, a live 24-hour broadcast will take place, with thousands of schools in 197 countries getting involved.
One project running in the build-up to the day uses Skype PeaceTalks, facilitated by Gilley, to connect students who live in very different places. The second talk was between Brentwood County High School in the UK and Gymnasium 164, a school in Zelenogorsk, Russia - a "closed town" with strict security procedures for entry (bit.lyPeaceTalkVideo).
"I passionately believe that educating young people is the key to building a united and sustainable world," Gilley says. "We must appeal to young people's sense of world citizenship."
For more information on the Poem for Peace competition, and to download an interactive lesson plan, poetry warm-up games and class activities, visit www.peaceoneday.orgresources.