# Days until St. Patrick’s Day

Counts the days from today, or any date you choose, to the next St. Patrick’s Day, with its date and day of the week.

- Page: https://www.acalculator.org/days/days-until-st-patricks-day
- JSON spec: https://www.acalculator.org/days/days-until-st-patricks-day.json
- Version: d8e7fb136f15

## Default answer

Example with the default inputs (Count from September 29, 2026) on the example date Tuesday, September 29, 2026: From September 29, 2026, there are 169 days until St. Patrick’s Day on Wednesday, March 17, 2027.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| from | Count from | The date to count from. Today, unless you change it. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| days | Days until St. Patrick’s Day | Whole days from the start date to the next St. Patrick’s Day; 0 on the day itself. |
| date | Date | The next date of St. Patrick’s Day on or after the start date. |
| weekday | Day of the week | The weekday of that date. |
| weeks | In weeks | The same number of days in weeks and days. |

## Method

Find the first date of St. Patrick’s Day on or after the start date, then count the days from the start date to it.

## Assumptions

- St. Patrick’s Day is March 17 every year.
- Start dates from January 1, 1900 to December 31, 2400 work, because the date field accepts that range.
- The start date itself is not counted: from the day before, the count is 1; on the day itself, it is 0.
- Dates are calendar days with no time of day, so a time zone or a daylight-saving change never adds or loses a day.

## Worked examples

1. from = 2026-01-01 gives date = 2026-03-17, days = 75. Source: the rule written again in Python 3 (datetime); docs/progress/WP-43.md.
2. from = 2026-03-18 gives date = 2027-03-17, days = 364. Source: the rule written again in Python 3 (datetime); docs/progress/WP-43.md.

## FAQ

### When is St. Patrick’s Day 2027?

St. Patrick’s Day 2027 is on Wednesday, March 17, 2027.

### When is St. Patrick’s Day 2028?

St. Patrick’s Day 2028 is on Friday, March 17, 2028.

### How is the date of St. Patrick’s Day set?

St. Patrick’s Day is March 17 every year. Source: the rule written again in Python 3 (datetime).

### How are the days until St. Patrick’s Day counted?

From the start date (today, unless you change it) to the date, without counting the start date. The day before, the count is 1; on the day itself, it is 0; the day after, the count moves on to the next St. Patrick’s Day.

## Sources

- the rule written again in Python 3 (datetime); docs/progress/WP-43.md