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javascript/snippets/day-of-year.md

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+---
+title: Day of year
+type: snippet
+tags: [date]
+cover: interior-3
+dateModified: 2020-10-19T18:51:03+03:00
+---
+
+Gets the day of the year (number in the range 1-366) from a `Date` object.
+
+- Use the `Date` constructor and `Date.prototype.getFullYear()` to get the first day of the year as a `Date` object.
+- Subtract the first day of the year from `date` and divide with the milliseconds in each day to get the result.
+- Use `Math.floor()` to appropriately round the resulting day count to an integer.
+
+```js
+const dayOfYear = date =>
+  Math.floor((date - new Date(date.getFullYear(), 0, 0)) / 1000 / 60 / 60 / 24);
+```
+
+```js
+dayOfYear(new Date()); // 272
+```