Date Tools — days between dates, calendars and day counters
Count days, working days and weeks between two dates, look up any date in history or in the future, and see how far away it is.
Calculators for questions about dates rather than the clock: how far apart two dates are, what date falls a given number of days out, which weekday a date lands on, and how many working days sit between two points.
Calculators
Months
Popular day counters
How to use Date Tools
Each tool takes one kind of question. Pick the one that matches what you are actually asking, because the same two dates can produce different correct answers depending on how you count them. Difference between two dates — you have a start and an end and want the span.
Add or subtract from a date — you have one date and an interval, and want where it lands. Day of the week — you have a date and want to know which day it is. Working days — you want the span with weekends taken out.
Enter dates in the order the tool asks for. If you reverse start and end, the difference will come back negative rather than silently flipping — that is deliberate, so a swapped pair is visible instead of invisible.
The inclusive counting problem
This is where most disagreements about dates come from, and it is not a bug in anyone's arithmetic. From Monday to Wednesday is two days if you count the gaps and three days if you count the days themselves. Both are defensible. The trouble starts when two people use different conventions and neither says which.
It matters most in deadlines. "Within 30 days" hangs entirely on whether day one is the day of the event or the day after it, and contracts, refund windows and notice periods are inconsistent about this. When the answer has consequences, find out which convention applies before you calculate rather than after.
A deadline is never just a date. It is a date plus a rule about how to count towards it, and the rule is usually written somewhere less convenient than the date.
Months and years are not fixed units
Adding days is unambiguous — a day is a day. Adding months is not, because months have different lengths, and there is no universally agreed answer to what "one month after the 31st" means when the next month is shorter.
Month lengths vary, so "three months" is a different number of days depending on which three months. A year is not always the same length; leap years carry an extra day. Adding a month to a date near the end of a month can land on a date that does not exist, and the result depends on the convention used to resolve it.
Adding a month and then another is not always the same as adding two at once, for the same reason. If precision matters, count in days. Days are the only unit here that never changes size.
Working days and what counts as one
The working-day calculator removes Saturdays and Sundays. It does not know about public holidays, which vary by country, by region within a country, and by year — some are fixed to a date, others move. Treat the result as the weekday count and then subtract whatever holidays apply where you are.
The same caution applies to the working week itself. Saturday and Sunday are not the weekend everywhere, so if you are counting business days across borders, confirm which days are non-working at the other end.
Questions and answers
- Why does my answer differ from someone else's by one day?
- Almost always inclusive versus exclusive counting — whether the first day is counted as day one or day zero. Agree on the convention and the difference disappears.
- Are public holidays included in the working-day count?
- No. Only weekends are removed. Holidays differ too much between places and years to assume, so subtract yours separately.
- Should I add months or add days?
- Days, whenever the exact result matters. Months vary in length, so adding them involves a convention; adding days involves none.