Event is the subject and occurred is the verb
The probability based on an event that has already occurred is 100%. If the event has occurred, it has occurred.
September 15, 1963 The Birmingham Church Bombing. Killed 4 little girls that were there for Sunday School.
The constitutional convention occurred second.
The Vietnam War is the event that occurred in the Tonkin Gulf.
September 25th 1963 was a Wednesday.
September 18, 1963 fell on a Wednesday.
September 3, 1963 was a Tuesday.
The probability of event A occurring given event B has occurred is an example of conditional probability.
September 11th 1963 was a Wednesday.
No memorable space event occurred on this day.
What important event occurred April 9th, 1865