1 files changed, 35 insertions, 0 deletions
diff --git a/date-fns/src/startOfQuarter/index.ts b/date-fns/src/startOfQuarter/index.ts
new file mode 100644
index 0000000..c61c2a0
--- /dev/null
+++ b/date-fns/src/startOfQuarter/index.ts
@@ -0,0 +1,35 @@
+import toDate from '../toDate/index'
+import requiredArgs from '../_lib/requiredArgs/index'
+
+/**
+ * @name startOfQuarter
+ * @category Quarter Helpers
+ * @summary Return the start of a year quarter for the given date.
+ *
+ * @description
+ * Return the start of a year quarter for the given date.
+ * The result will be in the local timezone.
+ *
+ * ### v2.0.0 breaking changes:
+ *
+ * - [Changes that are common for the whole library](https://github.com/date-fns/date-fns/blob/master/docs/upgradeGuide.md#Common-Changes).
+ *
+ * @param {Date|Number} date - the original date
+ * @returns {Date} the start of a quarter
+ * @throws {TypeError} 1 argument required
+ *
+ * @example
+ * // The start of a quarter for 2 September 2014 11:55:00:
+ * const result = startOfQuarter(new Date(2014, 8, 2, 11, 55, 0))
+ * //=> Tue Jul 01 2014 00:00:00
+ */
+export default function startOfQuarter(dirtyDate: Date | number): Date {
+  requiredArgs(1, arguments)
+
+  const date = toDate(dirtyDate)
+  const currentMonth = date.getMonth()
+  const month = currentMonth - (currentMonth % 3)
+  date.setMonth(month, 1)
+  date.setHours(0, 0, 0, 0)
+  return date
+}