Date Difference Calculator
Time between two dates, in every unit, with or without weekends.
How it works
Days between two dates is a subtraction of timestamps. Everything else follows from it, except the weekday count, which has to walk the calendar because week boundaries do not align with month or year boundaries.
Whether to count the end date depends on the question. "How many days until Friday" excludes it; "how many days am I on holiday" includes it.