Question: when did the country that developed the F-117 adopt Daylight Saving Time?

full_context: Document 1: Daylight saving time: New Zealander George Hudson proposed the modern idea of daylight saving in 1895. Germany and Austria-Hungary organized the first nationwide implementation, starting on 30 April 1916. Many countries have used it at various times since then, particularly since the energy crisis of the 1970s.
Document 2: Paul Gunn: After Japan's surrender in World War II, Gunn turned to rebuilding his Philippine Air Lines. The company provided flights across the south Paciific Ocean. Gunn died when his plane crashed in a storm over the Philippines on October 11, 1957. There were no survivors.
Document 3: Scott Speicher: Michael Scott Speicher (12 July 1957 – January 17, 1991) was a United States Navy pilot who was shot down over Iraq during the Persian Gulf War becoming the first American combat casualty of the war. His fate was not known until 2 August 2009 when the Navy reported that Speicher's remains were found in Iraq by United States Marines.
Document 4: History of unmanned aerial vehicles: Later, in November 1917, the Automatic Airplane was flown for representatives of the US Army. This led the army to commission a project to build an ``aerial torpedo '', resulting in the Kettering Bug which first flew in 1918. While the Bug's revolutionary technology was successful, it was not in time to fight in the war, which ended before it could be fully developed and deployed.
Document 5: Daylight saving time: Starting on 30 April 1916, Germany and its World War I ally Austria-Hungary were the first to use DST (German: Sommerzeit) as a way to conserve coal during wartime. Britain, most of its allies, and many European neutrals soon followed suit. Russia and a few other countries waited until the next year and the United States adopted it in 1918.
Document 6: United States Air Force: The fighter aircraft of the USAF are small, fast, and maneuverable military aircraft primarily used for air-to-air combat. Many of these fighters have secondary ground-attack capabilities, and some are dual-roled as fighter-bombers (e.g., the F-16 Fighting Falcon); the term "fighter" is also sometimes used colloquially for dedicated ground-attack aircraft. Other missions include interception of bombers and other fighters, reconnaissance, and patrol. The F-16 is currently used by the USAF Air Demonstration squadron, the Thunderbirds, while a small number of both man-rated and non-man-rated F-4 Phantom II are retained as QF-4 aircraft for use as Full Scale Aerial Targets (FSAT) or as part of the USAF Heritage Flight program. These extant QF-4 aircraft are being replaced in the FSAT role by early model F-16 aircraft converted to QF-16 configuration. The USAF has 2,025 fighters in service as of September 2012.
Document 7: Daylight saving time: After Germany led the way with starting DST (German: Sommerzeit) during World War I on 30 April 1916 together with its allies to alleviate hardships from wartime coal shortages and air raid blackouts, the political equation changed in other countries; the United Kingdom used DST first on 21 May 1916. US retailing and manufacturing interests led by Pittsburgh industrialist Robert Garland soon began lobbying for DST, but were opposed by railroads. The US's 1917 entry to the war overcame objections, and DST was established in 1918.
Document 8: Ben Rich: Benjamin Robert Rich (June 18, 1925 – January 5, 1995) was an American engineer and the second Director of Lockheed's Skunk Works from 1975 to 1991, succeeding its founder, Kelly Johnson. Regarded as the "father of stealth", Rich was responsible for leading the development of the F-117, the first production stealth aircraft. He also worked on the F-104, U-2, A-12, SR-71, and F-22, among others.
Document 9: Daylight saving time: George Hudson proposed the idea of daylight saving in 1895. The German Empire and Austria - Hungary organized the first nationwide implementation, starting on April 30, 1916. Many countries have used it at various times since then, particularly since the energy crisis of the 1970s.
Document 10: Daylight saving time: Starting on April 30, 1916, the German Empire and its World War I ally Austria - Hungary were the first to use DST (German: Sommerzeit) as a way to conserve coal during wartime. Britain, most of its allies, and many European neutrals soon followed suit. Russia and a few other countries waited until the next year, and the United States adopted it in 1918.
Document 11: Jameel Sayhood: Jameel Sayhood was an Iraqi pilot in the Gulf War who it is claimed managed to attain one of the few aerial victories by the Iraqi Air Force in his MiG-29B, before being shot down by USAF Captain Craig Underhill and Captain Cesar Rodriguez with their F-15Cs mere minutes after his air-air victory.
Document 12: AAI RQ-2 Pioneer: The AAI RQ-2 Pioneer is an unmanned aerial vehicle (UAV) that had been utilized by the United States Navy, Marine Corps, and Army, and deployed at sea and on land from 1986 until 2007. Initially tested aboard USS "Iowa", the RQ-2 Pioneer was placed aboard s to provide gunnery spotting, its mission evolving into reconnaissance and surveillance, primarily for amphibious forces.
Document 13: Lockheed MQM-105 Aquila: The Lockheed MQM-105 Aquila (Eagle) was the first small battlefield drone developed in the United States during the 1970s to act as a target designator for the US Army.
Document 14: IAI Scout: The IAI Scout (known in Israel under its Hebrew name זהבן - "Oriole") is a reconnaissance unmanned air vehicle developed in Israel in the 1970s by Israel Aircraft Industries as a competitor to the Tadiran Mastiff. During the 1970s, the Israeli military was becoming increasingly interested in battlefield UAVs, and in response IAI management finally decided that they were interested in the concept as well. The Scout had a similar configuration as the Mastiff, with a pusher propeller and a twin-boom tail.
Document 15: David P. Cooley: David Paul Cooley (February 15, 1960 – March 25, 2009) was a Lockheed test pilot and retired United States Air Force (USAF) officer, responsible for developmental flight testing of the F-117 Nighthawk. He was killed while flying a test mission in an F-22 Raptor jet fighter over the high desert of Southern California.
ground_truth: 1918
sub_queries: F-117 Nighthawk >> manufacturer Answer: Lockheed
Lockheed MQM-105 Aquila >> country Answer: the United States
What year did the United States finally adopt Daylight Saving Time? Answer: 1918