Datefold — every date question, answered exactly
Age, date differences, business days, countdowns and leap years — standard Gregorian arithmetic with the formula shown on every page. Free, no sign-up.
Age calculator
Exact age in years, months and days — plus your next birthday.
Date difference calculator
Exact days, weeks and months between any two dates.
Add or subtract days calculator
Add or subtract days, weeks, months or years.
Countdown calculator
Days until (or since) any date, in both directions.
Business days calculator
Monday–Friday count between two dates.
Day of week calculator
The weekday of any date, past or future.
Leap year checker
Is a year a leap year? The rule, applied.
Counting down now
Halloween 2026 — 47 daysThanksgiving (US) 2026 — 73 daysBlack Friday 2026 — 74 daysChristmas 2026 — 102 daysNew Year's Day 2027 — 109 daysValentine's Day 2027 — 153 days
Browse by year
Ages by birth year (1940–2015)Leap years 1900–2100Business days by year
Frequently asked questions
Is the calendar math here exact?
Yes — every page runs real Gregorian calendar arithmetic: true month lengths, the 4/100/400 leap rule and ISO-8601 week boundaries. No 365.25-day averages.
Do you store anything I enter?
No. Every calculator runs entirely in your browser; nothing is sent to a server, and there are no accounts.
Which holiday dates are computed by rule?
Fixed-date holidays (Christmas, New Year, Valentine's Day, Halloween, July 4) are constants. Thanksgiving and Black Friday follow the fourth-Thursday rule; Easter uses the Gregorian computus.