ToolWren"What date is 90 days from today?" "What was the date 6 weeks ago?" These come up constantly — for deadlines, notice periods, renewals and planning. Doing it in your head is error-prone because months have different lengths and leap years exist. Here is how to get it right every time.
Adding days to a date
To move forward, take your start date and add the number of days. The only trick is rolling over month and year boundaries correctly — adding 20 days to 25 January lands on 14 February, not the 45th of January. Our date add/subtract calculator does this instantly and also shows you the resulting day of the week.
Subtracting days (working backwards)
To find a past date, subtract instead. This is how you answer "if the deadline is the 30th and I need 10 working days' notice, when must I start?" Enter the amount and choose Subtract. This backwards, or "forward-dating in reverse", calculation is exactly what the tool is built for.
Weeks, months and years
You are not limited to days. Switch the unit to weeks, months or years and the calculator uses real calendar math. Adding one month to 31 January sensibly lands in February, and adding a year across 29 February handles the leap-year edge case for you — the kind of detail that trips up manual counting.
Counting the gap between two dates
The flip side of adding days is measuring the distance between two dates. For that, use the date difference calculator — it tells you how many days, weeks or months apart two dates are. To count only working days (excluding weekends), the business days calculator is the one you want.
Ages and anniversaries
A special case of date maths is working out an age or how long until an anniversary. The age calculator gives an exact years-months-days breakdown from any birth or start date. Every one of these tools runs entirely in your browser, so nothing you enter is uploaded.