fix(DatePicker, DateRangePicker): prevent set 1970-01-01T00:00:00.000Z date when initial dates are not set when using the cancel() method

Author: mrholek

js/src/date-range-picker.js

@@ -232,8 +232,8 @@ class DateRangePicker extends BaseComponent {
       return
     }
 
-    this._initialStartDate = new Date(this._startDate)
-    this._initialEndDate = new Date(this._endDate)
+    this._initialStartDate = this._startDate ? new Date(this._startDate) : null
+    this._initialEndDate = this._endDate ? new Date(this._endDate) : null
 
     EventHandler.trigger(this._element, EVENT_SHOW)
     this._element.classList.add(CLASS_NAME_SHOW)
@@ -274,15 +274,19 @@ class DateRangePicker extends BaseComponent {
   }
 
   cancel() {
-    this._changeStartDate(this._initialStartDate)
+    this.hide()
 
-    if (this._config.range) {
-      this._changeEndDate(this._initialEndDate)
+    if (this._initialStartDate) {
+      this._changeStartDate(this._initialStartDate)
     }
 
-    this.hide()
+    if (this._config.range && this._initialEndDate) {
+      this._changeEndDate(this._initialEndDate)
+    }
 
-    this._calendar.update(this._getCalendarConfig)
+    if (this._initialStartDate || this._initialEndDate) {
+      this._calendar.update(this._getCalendarConfig)
+    }
   }
 
   clear() {

js/src/util/calendar.js

@@ -268,7 +268,7 @@ const getTrailingDays = (year, month, leadingDays, monthDays) => {
  * @returns The ISO week number.
  */
 export const getWeekNumber = date => {
-  const tempDate = new Date(date.getTime())
+  const tempDate = new Date(date)
   tempDate.setHours(0, 0, 0, 0)
 
   // Thursday in current week decides the year