Title: Battles of Lexington and Concord
Content:  The battles of Lexington and Concord were the first military engagements of the American Revolutionary War. The battles were fought on April 19, 1775 in Middlesex County, Province of Massachusetts Bay, within the towns of Lexington, Concord, Lincoln, Menotomy (present-day Arlington), and Cambridge. They marked the outbreak of armed conflict between the Kingdom of Great Britain and its thirteen colonies in America. In late 1774, Colonial leaders adopted the Suffolk Resolves in resistance to the alterations made to the Massachusetts colonial government by the British parliament following the Boston Tea Party. The colonial assembly responded by forming a Patriot provisional government known as the 
Title: Battles of Lexington and Concord
Content: Greenwalt, Phillip S., and Robert Orrison. A Single Blow: The Battles of Lexington and Concord and the Beginning of the American Revolution, April 19, 1775. Emerging Revolutionary War Series. El Dorado Hills, CA: Savas Beatie, 2018. ISBN: 978-1-61121-379-9. 
Title: Battles of Lexington and Concord
Content:  In April 1925, the United States Post Office issued three stamps commemorating the 150th anniversary of the Battles at Lexington and Concord. The Lexington—Concord commemorative stamps were the first of many commemoratives issued to honor the 150th anniversaries of events that surrounded America's War of Independence. The three stamps were first placed on sale in Washington, D.C. and in five Massachusetts cities and towns that played major roles in the Lexington and Concord story: Lexington, Concord, Boston, Cambridge, and Concord Junction (as West Concord was then known). This is not to say that other locations were not involved in the battles. The events were also commemorated on the 1925 Lexington-Concord Sesquicentennial half dollar.
Title: Lexington Battle Green
Content:  The Lexington Battle Green, also known as Lexington Common, is the historic town common of Lexington, Massachusetts, United States. It was at this site that the opening shots of the Battles of Lexington and Concord were fired on April 19, 1775, starting the American Revolutionary War. Now a public park, the common is a National Historic Landmark.
Title: Lexington–Concord Sesquicentennial half dollar
Content:  The Battles of Lexington and Concord took place in those neighboring Massachusetts towns on April 19, 1775. The enmity between the British government and the American colonials that preceded the Revolutionary War had led, by early 1775, to militia groups, hostile to the British, being formed in the Boston area. These groups, under the control of Massachusetts leader John Hancock's Committee of Safety, were often dubbed minutemen for their readiness to assemble to fight at a moment's notice. Caches of munitions were stored at various towns for their use, including at Concord. The Secretary of State for the Colonies, Lord Dartmouth, instructed the British commander in Boston, General 
Title: Concord, Massachusetts
Content:  The Battle of Lexington and Concord was the first conflict in the American Revolutionary War. On April 19, 1775, a force of British Army regulars marched from Boston to Concord to capture a cache of arms that was reportedly stored in the town. Forewarned by Samuel Prescott (who had received the news from Paul Revere), the colonists mustered in opposition. Following an early-morning skirmish at Lexington, where the first shots of the battle were fired, the British expedition under the command of Lt. Col. Francis Smith advanced to Concord. There, colonists from Concord and surrounding towns (notably a highly drilled company from Acton led by Isaac Davis) repulsed a British detachment at the Old North Bridge and forced the British troops to retreat. Subsequently, militia arriving from across the region harried 
Title: Battles of Lexington and Concord
Content:  regulars proceeded on to Concord, where they broke apart into companies to search for the supplies. At the North Bridge in Concord, approximately 400 militiamen engaged 100 regulars from three companies of the King's troops at about 11:00am, resulting in casualties on both sides. The outnumbered regulars fell back from the bridge and rejoined the main body of British forces in Concord. The British forces began their return march to Boston after completing their search for military supplies, and more militiamen continued to arrive from the neighboring towns. Gunfire erupted again between the two sides and continued throughout the day as the regulars marched 
Title: Lexington–Concord Sesquicentennial half dollar
Content:  held by the British, and by then about 400 minutemen had assembled. Seeing the smoke from Concord, the colonials believed the town was being burned, and attempted to cross the bridge to succor it. The British fired on them but the colonials returned fire and defeated them. The British, who had gotten reinforcements once they realized the countryside was roused against them, began their march to Boston harassed by at least 2,000 militiamen who inflicted a steady toll by gunfire until the British gained the protection of the cannon near Boston. The encounters at Lexington and Concord were the first battles of what became the Revolutionary War.
Title: Concord Monument Square–Lexington Road Historic District
Content:  The Concord Monument Square–Lexington Road Historic District is an historic district in Concord, Massachusetts. Monument Square, at the center of the district, was laid out in 1635. The district includes a collection of well-preserved residential houses stretching along Lexington Street southeast from the square, and along Lowell northwest of the square. The square is prominently known as the site of British activities on April 19, 1775, the day of the Battles of Lexington and Concord which began the American Revolutionary War, and of earlier meetings by Massachusetts Patriots which were held in the First Parish Church and Wright's Tavern. The Tavern and the Ralph Waldo Emerson House, which stands near the eastern end of the district, are both National Historic Landmarks. The district was listed on the National Register of Historic Places in 1977.
Title: Buckman Tavern
Content:  The Battle of Lexington and Concord took form before dawn on April 19, 1775. Having received word that the regular army had left Boston in force to seize and destroy military supplies in Concord, several dozen militiamen gathered on the town common, and then eventually went to the tavern to await the arrival of the British troops. Definite word reached them just before sunrise, and Captain Parker's company of militia left the tavern to assemble in two ranks on the common. Following the arrival of the army, a single shot was fired; by whom, it is still unknown. With this shot, the American Revolutionary War began. Although best known as the headquarters of the militia, Buckman Tavern is also noteworthy as perhaps the busiest of Lexington's 18th-century taverns. It housed the first village store in Lexington, and later, in 1813, the first town post office.

Question: when did the battles of lexington and concord happen?
Answer: April 19, 1775.