Referencing day counts in Acts

Acts gives a good example of inclusive reckoning of days when reporting Peter's visit to Cornelius. After Cornelius's vision of an angel he sends messengers to Peter who returns with them to preach the gospel. Note the day count in Acts 10.

Day	A	B	C	D
Event	Cornelius's vision	Peter's vision	Leave Joppa	Arrive Caesarea
Comment	About the 9th hour of the day	The next day	The next day	the following day
Reference	10:3	10:9	10:23	10:24
Exclusive reckoning	0	1	2	3
Inclusive reckoning	1	2	3	4
Example	Monday	Tuesday	Wednesday	Thursday

All the days are accounted for from the time Cornelius first saw the vision. Peter talks with Cornelius about the same time of day as when Cornelius first saw the vision—the 9th hour.

About the 9th hour of the day he saw clearly in a vision an angel of God come in and say to him, "Cornelius."

"4 days ago, about this hour, I was praying in my house at the 9th hour, and behold, a man stood before me in bright clothing..."

Our culture uses exclusive reckoning. Let's say Day A was a Monday. When referencing Monday we would say

• on Tuesday: yesterday or 1 day ago;
• on Wednesday: the other day (though this is non-specific) or 2 days ago; and
• on Thursday: 3 days ago.

But Cornelius says 4 days ago. This means the counting starts with 1 not 0 in this instance. Presumably the use of "next day" and "following day" allows for "previous day" ie. yesterday. Referencing Monday we have

• on Tuesday: previous day;
• on Wednesday: 3 days ago; and
• on Thursday: 4 days ago.

This is a legitimate way of numbering days. However I am not certain that this is a consistent feature when referencing days, months and years throughout the Bible. Compare Mark and Luke.

And after 6 days Jesus took with him Peter and James and John, and led them up a high mountain by themselves. (Mark 9:2)

Now about 8 days after these sayings he took with him Peter and John and James and went up on the mountain to pray. (Luke 9:28)

The important thing is to be aware of it and allow for variable accounting of time in Scripture.