Date calculator
Add or subtract days, weeks, months or years from a date, or find the number of days between two dates — with the weekday, and the span in weeks, months and years, worked out alongside the headline number.
Add or subtract from a date
Days between two dates
Every date & age tool
Thirteen calculators sharing one calendar engine — pick the one built for exactly what you're asking.
Everyday date math
Calendar & week tools
Work & countdowns
Due date tools
Days from today & days ago
One page per common count, each worked out live from today's date in your browser.
Days from today
Days ago
How the dates are worked out
Every calculator on this site shares one date engine, built from scratch rather than borrowed from a library, so the same rules apply everywhere: leap years follow the standard Gregorian rule (divisible by 4, except century years unless divisible by 400 — so 2000 and 2024 are leap years, 1900 and 2100 are not), and adding a month or a year clamps an out-of-range day to the last real day of the target month, so Jan 31 plus one month is Feb 28 (or 29), never an invalid date rolled forward.
Questions
How do I add or subtract days from a date?
Pick a start date, choose add or subtract, enter a number, and pick the unit (days, weeks, months or years). Adding months or years keeps the same day of the month where possible and clamps to the last valid day when it doesn't exist — Jan 31 plus one month lands on Feb 28 (or Feb 29 in a leap year), not Mar 3.
How are the days between two dates counted?
By default the count is exclusive: Jan 1 to Jan 3 is 2 days, the number of nights or the number of times midnight passes. Switch on "inclusive" to count both the start and end date — the way you'd count days of a trip or a rental period — and Jan 1 to Jan 3 becomes 3.
Why does the years/months/days breakdown sometimes look different from just dividing the day count?
Because months don't all have the same number of days. 45 days is always "6 weeks 3 days," but it isn't always "1 month 15 days" — that depends on which month you're counting through. The calendar breakdown here counts whole months and years first, the way an age calculator does, then whatever's left over in days.
Does this account for leap years?
Yes, throughout — including the century rule (1900 and 2100 are not leap years, but 2000 and 2400 are, because only centuries divisible by 400 keep the leap day) and Feb 29 birthdays, which land on Feb 28 in non-leap years when you add whole years to them.
Is anything I enter saved?
No. Every calculation runs in your browser; nothing is sent to a server or stored.