# Correct
@manual{Smith2021b,
  author = {Smith, John},
  title = {AI in Development},
  date = {2021-12-01}
}

# Correct
@manual{Smith2021ba,
  author = {Smith, John},
  title = {somethingelse},
  date = {2021}
}

# False
@manual{Smith2021a,
  author = {Smith, John},
  title = {The Importance of},
  date = {12-12-2021}
}

# False
@manual{Smith2021c,
  author = {Smith, John},
  title = {The AI in Software Development},
  date = {2021-21-12}
}

# False
@manual{Smith2021ca,
  author = {Smith, John},
  title = {Unknown Month only is invalid for sure},
  date = {2021-21}
}

# False
@manual{Smith2021cb,
  author = {Smith, John},
  title = {Unknown Day only is invalid too},
  date = {2021-01}
}