Question 1

How are the total days counted?

Accepted Answer

Both dates are treated as plain calendar dates in UTC, so the count never shifts by a day because of time zones or daylight saving. The result is elapsed days: 1 January to 2 January counts as 1 day.

Question 2

What does Y / M / D mean?

Accepted Answer

It is the calendar distance between the two dates, for example 1 year 2 months 14 days. Month ends are clamped: 31 January plus one month is 28 or 29 February.

Question 3

Are public holidays deducted from business days?

Accepted Answer

No. Only Saturdays and Sundays are excluded, so the business-day count is an upper bound. Subtract your local public holidays if you need an exact working-day figure.