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node_modules/date-fns/differenceInYears.js

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+"use strict";
+exports.differenceInYears = differenceInYears;
+var _index = require("./compareAsc.js");
+var _index2 = require("./differenceInCalendarYears.js");
+var _index3 = require("./toDate.js");
+
+/**
+ * @name differenceInYears
+ * @category Year Helpers
+ * @summary Get the number of full years between the given dates.
+ *
+ * @description
+ * Get the number of full years between the given dates.
+ *
+ * @typeParam DateType - The `Date` type, the function operates on. Gets inferred from passed arguments. Allows to use extensions like [`UTCDate`](https://github.com/date-fns/utc).
+ *
+ * @param dateLeft - The later date
+ * @param dateRight - The earlier date
+ *
+ * @returns The number of full years
+ *
+ * @example
+ * // How many full years are between 31 December 2013 and 11 February 2015?
+ * const result = differenceInYears(new Date(2015, 1, 11), new Date(2013, 11, 31))
+ * //=> 1
+ */
+function differenceInYears(dateLeft, dateRight) {
+  const _dateLeft = (0, _index3.toDate)(dateLeft);
+  const _dateRight = (0, _index3.toDate)(dateRight);
+
+  const sign = (0, _index.compareAsc)(_dateLeft, _dateRight);
+  const difference = Math.abs(
+    (0, _index2.differenceInCalendarYears)(_dateLeft, _dateRight),
+  );
+
+  // Set both dates to a valid leap year for accurate comparison when dealing
+  // with leap days
+  _dateLeft.setFullYear(1584);
+  _dateRight.setFullYear(1584);
+
+  // Math.abs(diff in full years - diff in calendar years) === 1 if last calendar year is not full
+  // If so, result must be decreased by 1 in absolute value
+  const isLastYearNotFull =
+    (0, _index.compareAsc)(_dateLeft, _dateRight) === -sign;
+  const result = sign * (difference - +isLastYearNotFull);
+
+  // Prevent negative zero
+  return result === 0 ? 0 : result;
+}