Divide the words into 3 groups according to the prepositions of time we use before them

• Группы
  • in
  • on
  • at
• Варианты
  • 2017
  • the 1st of July
  • the weekend
  • the morning
  • July
  • summer
  • the afternoon
  • the 20th century
  • night
  • Christmas
  • 7 o'clock
  • half past six
  • weekdays
  • Friday
  • Saturday morning
  • Christmas Day
  • a warm summer day
  • midnight
  • noon