The unofficial holiday, National Surprise Drug Test Day, began as an answer to another unofficial holiday called National Marijuana or Weed Day, which occurs every year on April 20. When parents and companies caught on to the fact that April 20 was Marijuana Day, they would carry out drug tests on their children or employees the following day. Employees who test positive for the substance might be at risk of losing their jobs.
This has become the subject of heated debates and advocacy groups for the legalization of marijuana argue against the unfairness of letting go of employees merely on the basis that they are marijuana users. This is especially so in states where marijuana use is legal.
Source of information NCA/PDA