1 files changed, 38 insertions, 0 deletions
diff --git a/date-fns/src/_lib/setUTCDay/index.js b/date-fns/src/_lib/setUTCDay/index.js
new file mode 100644
index 0000000..6e4e472
--- /dev/null
+++ b/date-fns/src/_lib/setUTCDay/index.js
@@ -0,0 +1,38 @@
+import toInteger from '../toInteger/index'
+import toDate from '../../toDate/index'
+import requiredArgs from '../requiredArgs/index'
+
+// This function will be a part of public API when UTC function will be implemented.
+// See issue: https://github.com/date-fns/date-fns/issues/376
+export default function setUTCDay(dirtyDate, dirtyDay, dirtyOptions) {
+  requiredArgs(2, arguments)
+
+  var options = dirtyOptions || {}
+  var locale = options.locale
+  var localeWeekStartsOn =
+    locale && locale.options && locale.options.weekStartsOn
+  var defaultWeekStartsOn =
+    localeWeekStartsOn == null ? 0 : toInteger(localeWeekStartsOn)
+  var weekStartsOn =
+    options.weekStartsOn == null
+      ? defaultWeekStartsOn
+      : toInteger(options.weekStartsOn)
+
+  // Test if weekStartsOn is between 0 and 6 _and_ is not NaN
+  if (!(weekStartsOn >= 0 && weekStartsOn <= 6)) {
+    throw new RangeError('weekStartsOn must be between 0 and 6 inclusively')
+  }
+
+  var date = toDate(dirtyDate)
+  var day = toInteger(dirtyDay)
+
+  var currentDay = date.getUTCDay()
+
+  var remainder = day % 7
+  var dayIndex = (remainder + 7) % 7
+
+  var diff = (dayIndex < weekStartsOn ? 7 : 0) + day - currentDay
+
+  date.setUTCDate(date.getUTCDate() + diff)
+  return date
+}