When is our 100 days anniversary?

If the day you met counts as day 1, it is 99 days after that date. Switch on "Count the first day as day 1" and enter the date; the "Milestones" table shows day 100 with its weekday.

What date is 100 days from today?

Press "100 days from today" to fill in that date and see its weekday. It is the 100th day counted from tomorrow.

Does a days until countdown include today?

No. If today is the 1st and the date is the 10th, it shows D-9.

Is the day itself D-0 or D-Day?

It is shown as D-Day, and the following days count up as D+1, D+2. With "Count the first day as day 1" on, the date itself is day 1.

How many years is 1000 days?

About 2 years and 9 months. From January 1, 2026, 1,000 days later is September 27, 2028, which is 2 years, 8 months and 26 days.

Is a one year anniversary the same as 365 days?

Not always. The anniversary is the same date a year later, so it is 365 or 366 days after the start, or day 366 or 367 if the start counts as day 1.

Can I count only weekdays until a date?

Yes, "Weekdays (no weekends)" shows the number of Mondays to Fridays. Public holidays are not removed, so subtract them yourself for business days.

Can I save more than one countdown?

Yes. Each press of "Save to list" adds the date to "Saved dates", sorted nearest first. The list stays in this browser and does not sync to other devices.

How do I share a countdown with someone?

Press "Copy link" to copy a link that holds the date and the title. Whoever opens it sees the same countdown, worked out for their own today.

Days Until & Days Since Calculator

Count how many days until an exam, trip or birthday, or the days since a date. Shows 100 days from today, day 1000, anniversary dates and weekdays left.

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This days until calculator counts the days left before a coming date such as an exam, a trip or a wedding (D-n), or the days since a past date such as the day you met or a baby's birth (D+n). You can count the start date itself as day 1, as Korean couples do, and a table lists the date and weekday of every milestone from day 100 to day 10,000 and every anniversary up to year 30. It also shows the gap in weeks, in months and in weekdays without weekends, and you can save several countdowns or share one as a link.

How to use

Enter a name such as exam, trip or anniversary under "Title" and pick the "Date". A coming date shows D-n in large type, a past date D+n.
Instead of picking a date, you can press "100 days from today", "100 days ago" or "Today" to fill in the date field.
Check the weekday of the date and the results "In weeks", "In months" and "Weekdays (no weekends)".
To count the date itself as the first day, as couples and parents often do, switch on "Count the first day as day 1". It applies to past dates only.
In the "Milestones" table, read the date, weekday and distance from today of every 100th day and every anniversary. The highlighted row is the next one, and "Show more" opens the list up to year 30 and day 10,000.
Keep dates you check often with "Save to list", and press "Copy link" to send one to someone.

How it works

For a coming date, days are counted from tomorrow up to the date, leaving today out. A date that is tomorrow shows D-1, and the date itself shows D-Day.
For a past date, counting starts the day after by default. With "Count the first day as day 1" on, the date is day 1, so the result is one larger and day 100 falls 99 days after the date.
"Weekdays (no weekends)" counts Monday to Friday only. Public holidays are not removed, so it can differ from real working or business days.
Anniversaries fall on the same month and day each year. If the start date is February 29, anniversaries in non-leap years are shown on February 28.
Up to 100 saved dates stay only in this browser on this device, listed nearest to today first. A copied link contains the date and the title.

Days since we met: count from day 1 or day 0?

In Korea, couples usually count the day they met as day 1. With that rule, day N falls N − 1 days after the start, so a relationship that began on January 1, 2026 reaches day 100 on April 10, 2026, which is 99 days later. A baby's hundredth day is often counted the same way, with the birth date as day 1.

When you count a period, such as 100 days from today, the start date is left out and counting begins the next day. From the same January 1, day 100 lands on April 11, one day later. This tool uses that rule by default; switch on "Count the first day as day 1" for the first rule, and every date in the "Milestones" table moves one day earlier. Neither is wrong, so agree on one with the person you are celebrating with.

How many days until a date: how the countdown works

The n in D-n is the number of days left, not counting today, which is simply the difference between the two dates. If today is March 1 and the exam is on March 31, 31 − 1 = 30, so it shows D-30. The date itself is D-Day and the day after is D+1. Months have 28 to 31 days, which makes counting by hand error-prone; this tool counts by date difference and handles leap years.

Seeing the gap in other units helps with planning. The 30 days above are 4 weeks and 2 days, and in 2026 the Monday-to-Friday days from March 2 to March 31 add up to 22 weekdays. For a study or work plan, weekdays are closer to the days you can really use, but public holidays still need to be taken off by hand.

Day 100, day 1000 and anniversary dates at a glance

The "Milestones" table lists every 100th day up to day 1,000, then day 1,500 and every 1,000th day from 2,000 to 10,000, plus anniversaries from year 1 to year 30, in date order. At first it shows only the first three years and the next four milestones; "Show more" opens the whole list.

For example, with January 1, 2026 as day 1, day 100 is April 10, day 200 is July 19, day 300 is October 27 and day 1,000 is September 26, 2028, while the first anniversary is January 1, 2027. Because an anniversary is the same date a year later, it is usually day 366 when the start counts as day 1, or day 367 when a February 29 falls in between. Day 1,000 comes about 2 years and 9 months after the start.

Questions and answers

When is our 100 days anniversary?: If the day you met counts as day 1, it is 99 days after that date. Switch on "Count the first day as day 1" and enter the date; the "Milestones" table shows day 100 with its weekday.
What date is 100 days from today?: Press "100 days from today" to fill in that date and see its weekday. It is the 100th day counted from tomorrow.
Does a days until countdown include today?: No. If today is the 1st and the date is the 10th, it shows D-9.
Is the day itself D-0 or D-Day?: It is shown as D-Day, and the following days count up as D+1, D+2. With "Count the first day as day 1" on, the date itself is day 1.
How many years is 1000 days?: About 2 years and 9 months. From January 1, 2026, 1,000 days later is September 27, 2028, which is 2 years, 8 months and 26 days.
Is a one year anniversary the same as 365 days?: Not always. The anniversary is the same date a year later, so it is 365 or 366 days after the start, or day 366 or 367 if the start counts as day 1.
Can I count only weekdays until a date?: Yes, "Weekdays (no weekends)" shows the number of Mondays to Fridays. Public holidays are not removed, so subtract them yourself for business days.
Can I save more than one countdown?: Yes. Each press of "Save to list" adds the date to "Saved dates", sorted nearest first. The list stays in this browser and does not sync to other devices.
How do I share a countdown with someone?: Press "Copy link" to copy a link that holds the date and the title. Whoever opens it sees the same countdown, worked out for their own today.