Days Until

Days until or since any date, with the counting rule shown. Count the days until, or since, any date, and see which counting rule produced the number. Working days, milestones and several dates at once, all in your browser.

Try one:

Inclusive and exclusive counting, and why your answer is off by one

Two people counting the same two dates routinely get two numbers one apart, and both are right. Inclusive and exclusive counting disagree by exactly one day, which is where almost every argument about a countdown comes from. Every sentence this page hands you to copy names the rule it used.

Read the full explanation: the two rules, working days, milestones and time zones

Two people counting the same two dates routinely get two numbers one apart, and both are right. The disagreement is never arithmetic. It is about whether the first day of the span counts as a day.

  • Exclusive counting, the default here. Count the day boundaries crossed, which is the same as counting the nights between the two dates. The earlier of the two days is not itself counted. From 1 March to 4 March is three days. This is what a countdown means when it says three days to go, what a delivery estimate means, and what the D notation means: D-3 is three days before the day, D-Day is the day itself, and D+3 is three days after it.
  • Inclusive counting. Count both the first and the last day, so the first day is day one. From 1 March to 4 March is four days. This is how hotel and hospital day counts, court filing deadlines in many jurisdictions, and Korean relationship anniversaries work. It is the reason a couple celebrates day 100 on a date that is only ninety nine days after they started: under inclusive counting the starting day was already day one.

The two rules always differ by exactly one day, so the fix is never to argue about the number. State the rule alongside it. Every sentence this page hands you to copy names the rule it used.

Working days

With working days switched on, the same span is counted again with Saturdays and Sundays taken out. The span is identical, only the days inside it are filtered, so the inclusive and exclusive rules still apply in the same way. Public holidays are not deducted, because they differ by country and by year and this page ships no holiday calendar. Treat the working day figure as an upper bound.

Milestones

Milestone dates follow the rule you picked, which is exactly where they go wrong elsewhere. Under exclusive counting, day 100 falls one hundred days after the date. Under inclusive counting it falls ninety nine days after, because the date itself was day one. Year milestones are calendar based instead of day based, so one year after 3 September is 3 September, whatever leap years fall in between. A 29 February date has no 29 February in a common year, and the anniversary is shown on 28 February and flagged as moved.

Time zones

Every figure here comes from calendar arithmetic on the year, month and day you typed. Nothing is converted to or from UTC at any point, which is the usual source of a countdown that is a day out for readers east or west of whoever built it. The day the page counts from is read once from your device clock as a local calendar date, and you can override it in the field above to check any pair of dates without changing your clock.

What it costs and what it keeps

Free, no sign up, and your dates never leave your browser. Nothing here is uploaded and nothing is stored on a server: the list you build lives in this page and in the address bar of this tab.

Several dates at once

Add as many dates as you want to track. Rows live in this page and in the address bar only, so the address bar is the whole save function: copy the address and the same list comes back.

What it is Date Count

Milestones

Day milestones are placed by the counting rule selected above. Year milestones are calendar based.

Milestone Date Weekday Where it sits

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