# How many days since a date?

Counts the calendar days from a past date up to today or another end date, also as weeks and days, as years, months, and days, and as a day number.

- Page: https://www.acalculator.org/days/days-since-calculator
- JSON spec: https://www.acalculator.org/days/days-since-calculator.json
- Version: fb66dd77e8b3

## Default answer

Example with the default inputs (Start date June 22, 2026, Count up to September 30, 2026) on the example date Wednesday, September 30, 2026: 100 days since June 22, 2026.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| start | Start date | The past date to count from. |
| end | Count up to | The date to count up to. Today, unless you change it. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| days | Days since | Calendar days from the start date up to the end date: the end date minus the start date. |
| weeks | In weeks | The days as whole weeks and the days left. |
| span | In years, months, and days | The time from the start date to the end date as whole years, then whole months, then days. |
| dayNumber | Day number | The end date’s number when the start date is day 1: the days since plus 1. |
| weekday | Start date was a | The day of the week of the start date. |

## Method

days since = end date − start date, in whole calendar days (the start date is not counted, the end date is)

## Assumptions

- Dates are whole calendar days in the Gregorian calendar, with no time of day, so daylight-saving changes cannot add or lose a day.
- The count is the end date minus the start date: from yesterday to today is 1 day, and the same date twice is 0 days.
- The end date is today unless you change it; the page reads today’s date from your device when it loads.
- A start date after the end date has no answer.

## Worked examples

1. start = 2026-01-01, end = 2026-09-30 gives days = 272, weeks = {"weeks":38,"days":6}, span = {"years":0,"months":8,"days":29}, dayNumber = 273, weekday = Thursday. Source: Julian Day numbers (Meeus, Astronomical Algorithms, 1991, chapter 7): JD 2461313.5 − JD 2461041.5 = 272.
2. start = 2024-02-28, end = 2024-03-01 gives days = 2, dayNumber = 3, weekday = Wednesday. Source: Gregorian leap-year rule (ISO 8601).
3. start = 2000-01-01, end = 2026-09-30 gives days = 9,769, span = {"years":26,"months":8,"days":29}, weekday = Saturday. Source: Julian Day numbers (Meeus, Astronomical Algorithms, 1991, chapter 7): JD 2461313.5 − JD 2451544.5 = 9769.
4. start = 2026-09-30, end = 2026-09-30 gives days = 0, weeks = {"weeks":0,"days":0}, dayNumber = 1.

## FAQ

### How do I count the days since a date?

Subtract the start date from today, in whole calendar days. From January 1, 2026 to September 30, 2026 is 272 days: 30 days to January 31, then 212 days for February to August (28 + 31 + 30 + 31 + 30 + 31 + 31), then 30 days for September.

### Does the count include the start date?

No. The count is the days that have passed, so from yesterday to today is 1 day and from today to today is 0 days. If you number the days with the start date as day 1, today is the day number shown, which is the count plus 1.

### Are leap years counted?

Yes. The calculator uses the Gregorian calendar, so February has 29 days in years divisible by 4, except century years not divisible by 400. From February 28 to March 1, 2024 is 2 days.

### Why does the answer change when I open the page on another day?

The end date starts as today, read from your device when the page loads. The page itself was built on an earlier day, so it shows that day’s count until your browser works out today’s. Pick an end date if you want a fixed count.

### Can I count days since a date in the future?

No. If the start date is after the end date there is no answer. To count the days to a coming date, use a days until or days between dates calculator.

### How is the count shown in years, months, and days?

From the start date, the calculator takes the most whole years, then the most whole months, then the days left. From January 1, 2000 to September 30, 2026 is 26 years, 8 months, and 29 days.

## Sources

- Jean Meeus, Astronomical Algorithms (1991), chapter 7: Julian Day numbers, so the days between two dates are the difference of their Julian Days.
- ISO 8601, Date and time format: the Gregorian calendar and its leap-year rule.