How the difference is counted
The total number of days is the number of midnights between the two dates, so from Monday to Friday of the same week is 4 days. Turn on “include end date” to count both the first and last day, which gives 5; this is common for holidays, hire periods and project durations.
The years, months and days breakdown counts whole calendar years first, then whole months, then the remaining days. Because months have different lengths, the same number of days can produce a different month count depending on the start date.
Weekdays
Weekdays are Monday to Friday. Public holidays differ by country and are not removed, so subtract them yourself when counting working days.
Leap years
Leap years are handled automatically. A year is a leap year if it is divisible by 4, except century years, which must be divisible by 400.