Significance of April 22 Earth Day

Nelson chose the date in order to maximize participation on college campuses for what he conceived as an "environmental teach-in". He determined the week of April 19–25 was the best bet as it did not fall during exams or spring breaks. Moreover, it did not conflict with religious holidays such as Easter or Passover, and was late enough in spring to have decent weather. More students were likely to be in class, and there would be less competition with other mid-week events—so he chose Wednesday, April 22.
Unbeknownst to Nelson, April 22, 1970, was coincidentally the 100th anniversary of the birth of Vladimir Lenin. Time reported that some suspected the date was not a coincidence, but a clue that the event was "a Communist trick", and quoted a member of the Daughters of the American Revolution as saying, "subversive elements plan to make American children live in an environment that is good for them." J. Edgar Hoover, director of the U.S. Federal Bureau of Investigation, may have found the Lenin connection intriguing; it was alleged the FBI conducted surveillance at the 1970 demonstrations. The idea that the date was chosen to celebrate Lenin's centenary still persists in some quarters, an idea borne out by the similarity with the subbotnik instituted by Lenin in 1920 as days on which people would have to do community service, which typically consisted in removing rubbish from public property and collecting recyclable material. Subbotniks were also imposed on other countries within the compass of Soviet power, including Eastern Europe, and at the height of its power the Soviet Union established a nation-wide subbotnik to be celebrated on Lenin's birthday, April 22nd, which had been proclaimed a national holiday celebrating communism by Nikita Kruschev in 1955.

In Nebraska, Arbor Day falls on April 22, that being the birthday of Julius Sterling Morton, the founder of the national tree-planting holiday that started in 1872, which has been a legal holiday in the state since 1885. According to the National Arbor Day Foundation "the most common day for the state observances is the last Friday in April ... but a number of state Arbor Days are at other times in order to coincide with the best tree-planting weather." It has since been largely eclipsed by the more widely observed Earth Day, except in Nebraska, where it originated.