Question 1

How do I add days to a date?

Accepted Answer

Enter your start date and type the number of days to add in the Days field, then click Calculate. The result date appears instantly with the weekday name. Enter a negative number to subtract days instead.

Question 2

How does adding months work when the result month has fewer days?

Accepted Answer

When you add months and the resulting month is shorter than the start month, the date is clamped to the last day of that month. For example, 31 January + 1 month = 28 February (or 29 in a leap year). This is standard calendar-safe month arithmetic — the same behaviour as most date libraries.

Question 3

Can I add negative values to subtract time?

Accepted Answer

Yes. Enter a negative number in any field to subtract that unit. -7 days subtracts a week, -1 year subtracts a year. The result is the same as using the subtraction direction.

Question 4

How are years and months different from weeks and days?

Accepted Answer

Years and months are calendar units — their exact length varies (months have 28–31 days, years have 365 or 366). Weeks and days are fixed durations. The calculator applies year/month arithmetic on the calendar first, then adds any day offset — matching the behaviour of most programming date libraries.

Question 5

What day of the week will a date fall on?

Accepted Answer

The result date shows the full weekday name (Monday, Tuesday, etc.) so you can instantly check whether a deadline, meeting, or event lands on a weekend or a working day.

Question 6

Is my data safe here?

Accepted Answer

Yes. Date arithmetic runs in your browser. Nothing is sent to a server.

Date calculator

How date math works here