Date Math
Simple, human-friendly date calculations
No accounts. No clutter. Just dates — calculated privately in your browser.
A free online date calculator
Date Math answers the everyday date questions that are surprisingly fiddly to do in your head — adding days to a deadline, counting business days for an invoice, or finding the end of the quarter. Pick a tool below, or read the guides to see how each calculation works.
Calculators
Add / Subtract
Move any date forward or backward by days, weeks, or months — calendar or business days.
From Now
Find the date a set amount of time from today, or work out what the date was that long ago.
Between Dates
Count the days, weeks, or business days between two dates and copy a ready-made sentence.
Next / End Of
Jump to the next weekday or business day, or the end of the current month, quarter, or year.
Popular guides
All guidesHow to Calculate Business Days
What counts as a business day, how weekends and public holidays change the math, and how to add or count working days correctly.
How to Count the Days Between Two Dates
Inclusive vs. exclusive counting, converting days into weeks, and the everyday questions a days-between calculation answers.
Adding and Subtracting Days, Weeks, and Months
How date arithmetic really works, the month-end edge cases that trip people up, and when to switch to business-day mode.
Finding the End of a Month, Quarter, or Year
Locate period boundaries and the next weekday or business day — the dates that drive billing cycles, payroll, and reporting.