Should you include the start date?
From June 1 to June 10 is 9 days apart, but 10 days if you count June 1 itself. Which one you need depends on the question:
- Include it for things counted as “day 1, day 2”: days worked, length of a trip or a hotel stay in days, a 30-day challenge.
- Leave it out for the gap between dates: days until a deadline, interest periods, age.
The countdown shows the plain difference from today, so a date tomorrow shows D-1.
How months are counted
A month passes each time the same day of the month comes round. When that day doesn't exist (one month after January 31), we use the last day of the month instead, so January 31 + 1 month is February 28, or 29 in a leap year. Adding months or years uses the same rule.
Weekdays leave out Saturdays and Sundays but not public holidays, so subtract any holidays yourself if you need exact business days.
FAQ
What date is 90 days from today?
Use “Add or subtract”: the start date is today by default, so enter 90 days after. This is handy for return windows, notice periods and visa stays.
Are my dates saved?
No. Everything is calculated in your browser and nothing is sent to a server.