This is a continuation of another idea, which is to include days of the week, weekday and weekend to the datediff function, that idea can be found here:
I separated this piece because I believe the implementation would be more difficult (ambiguous) but counting holidays or workdays between two dates would be useful. Using something like
datediff('holiday', [Date1], [Date2])
datediff('workday', [Date1], [Date2])
This could differ a lot regionally, but there is already a workbook locale which could control this to some degree. I'm not sure there is a clear definition of holiday, there are days that most people are off from work, days many children are off from school and days the post office is closed, but these aren't always consistently applied so it would be useful for users to have more control over this feature than locale. Maybe provide a way to select holidays from a checklist (like with map layers) or even just provide a way to input a list of holidays to be considered as with custom geocoding. That would allow the inclusion of personal holidays like birthdays if you wanted to do some analysis on how much cake you were eating at work in an average year... I'm not sure I want to know that one, but there are practical use cases too, such as organizational shutdowns, retreats, layoffs etc. Holidays might be the wrong word in this case, but the idea is the same, having some way to distinguish and count the number of exception days between two dates.
Maybe the keyword could be defined within the date list, so that multiple lists could be in play at once.
--> Community Manager update [Ciara Brennan]
Also refer to Duplicate idea #10341