Date Difference Calculator
Calculate the difference between two dates. Add or subtract days, weeks, months, years. Free, in your browser.
Why this matters
Date math is deceptively complex. Months have different lengths, leap years happen every 4 years (except every 100, except every 400), and time zones can shift a calculation by a day. Mental math for “how many days between March 15 and August 3” or “what's 90 days from today” is error-prone.
This calculator handles three common problems: how many days between two dates (useful for notice periods, project durations, age calculations), add or subtract days/weeks/months/years from a date (useful for “due in 30 days” calculations), and business day calculations (excluding weekends, useful for delivery estimates).
Best uses: calculating notice periods, project deadlines, visa expiry warnings, subscription renewals, baby due dates, and any other date arithmetic that would take a minute in a calendar app.
Between Two Dates
Add / Subtract from a Date
Frequently Asked Questions
What's this for?
Calculate time between two events (project duration, age in days, countdown to a deadline), or find a future/past date by adding weeks, months, or years.
Are weekends and holidays counted?
All days are counted equally. For business-day calculations, this tool doesn't apply.
Time zone?
Uses your browser's local timezone. The date inputs are calendar dates, not timestamps.