Excel – Calculating the number of days between two dates in Excel

datedate timemicrosoft excel

I consider 7 days to be a week,
so if I look at 1 January 2019 – 7 January 2019,
I would say that is 7 days. 
But often I seen when people are calculating the number of days between two dates or age they use the formula B1-A1 where A1 is the Start Date/DoB
and B1 is the end date or today's date. 
This would give 6 for the above example.

I use (B1-A1)+1 which gives 7
and for dates of birth I would use ((B1-A1)+1)/365.25. 
Which is correct?

Best Answer

It is not a question of one formula being right and the other being wrong. It is a question of what you are looking for.

Say you are working on a task 24 hours a day. You begin the task 17 January 2000 at 9:00 AM and complete the task 18 January 2000 at 9:00 AM. If the question is How many days did the task take ? You would take the difference; get 24 hours and answer 1 day.

If, however, the question is On how many days did you work on the task ? You would immediately respond 2

Thus =B1 - A1 or =B1 - A1 + 1 might be appropriate depending on what you are trying to measure.

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