Date Calculator
Add or subtract days, weeks, months or years from any date.
About this calculator
Counting forward or backward across the calendar is deceptively hard because months have 28 to 31 days and leap years shift everything by a day. This calculator does it precisely: pick a start date, choose to add or subtract, enter any mix of years, months, weeks and days, and it returns the exact resulting date and weekday.
It's the right tool for deadlines and planning — a 90-day return window, a 6-week notice period, a payment due 'net 30', a contract that runs two years from signing, or simply what date falls 100 days from today. Because it uses real calendar arithmetic rather than a flat 30-days-a-month shortcut, the answer is accurate even across month and year boundaries.
For the reverse question — how many days lie between two dates you already know, or someone's exact age — use the age & date-difference calculator instead. Both run entirely in your browser, so nothing you enter is stored or sent anywhere.
Frequently asked questions
Does the date calculator account for leap years?
Yes. Adding or subtracting across February 29 is handled correctly, so results spanning leap years are accurate.
Can I add months and days at the same time?
Yes. Enter any combination of years, months, weeks and days; they are all applied together to the start date.
How do I find the number of days between two dates?
Use the age & date-difference calculator, which measures the exact gap between two dates. This tool is for adding or subtracting a length of time from one date.