Whit Sunday
Many Christians all over the world annually observe Pentecost, also known as Whitsunday or Whit Sunday.
Elsewhere on timeanddate.com
Whit Monday
Whit Monday, or Pentecost Monday, is a Christian holiday that falls on the day after Pentecost, which is also known as Whit Sunday or Whitsunday.
AM and PM Explained
How does the 12-hour clock system work? Is midnight 12 am or 12 pm?
Daylight Saving Time (DST)
Why do many countries set the clocks back and forth an hour twice a year?