Date Calculator guide
Date Calculator: Add or Subtract Days, Weeks, Months and Years
Use our date calculator to add or subtract years, months, weeks and days from any date and find the day of the week it lands on.
By the AllCalculator editorial teamUpdated 16 October 20261 min read
What's the date 90 days from now, or 6 months before a deadline? Our Date Calculator works it out in a second.
How to use the calculator (Date Calculator)
- Choose a start date, or leave it blank to use today.
- Choose add or subtract.
- Enter any number of years, months, weeks and days.
You'll see the new date, its day of the week and how many days away it is.
How months are added
Months have different lengths, so the calculator adds the months first and keeps the same day of the month. If that day doesn't exist, it uses the last day of the month:
- 15 January + 1 month = 15 February
- 31 January + 1 month = 28 February (or 29 in a leap year)
Weeks and days are then added on top.
A worked example
With the calculator's default settings, if today is Friday 16 October 2026, adding 6 months gives Friday 16 April 2027, which is 182 days later.
Frequently asked questions
How do I count working days?
Use our Days Calculator, which skips weekends and UK bank holidays.
Does it handle leap years?
Yes. 2028 is the next leap year, with 29 February.
How do I count the days between two dates?
The Days Calculator does that too. To find out what day a date falls on, try our Day of the Week Calculator.
Sources and further reading
Links open official and independent websites in a new tab.
This guide is general information to help you understand your options. It isn't financial, tax, legal or building advice and doesn't take your personal circumstances into account. Figures were checked when the guide was last updated and can change, so confirm anything important with GOV.UK, HMRC, a regulated adviser or a qualified tradesperson.