From 8f0068227e848b29e3c53da5f7ab185c40f05a3a Mon Sep 17 00:00:00 2001
From: martakostova <arta.kostova@gmail.com>
Date: Fri, 18 Mar 2022 09:24:44 -0400
Subject: [PATCH 1/2] update getWeek because it returned wrong week N

---
 src/components/dateformat.js | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/src/components/dateformat.js b/src/components/dateformat.js
index 6669cde3..e6fefc66 100644
--- a/src/components/dateformat.js
+++ b/src/components/dateformat.js
@@ -150,7 +150,8 @@ function pad (val, len) {
  * @param  {Object} `date`
  * @return {Number}
  */
-function getWeek (date) {
+function getWeek (currentDate = new Date()) {
+  /*
   // Remove time components of date
   var targetThursday = new Date(date.getFullYear(), date.getMonth(), date.getDate());
 
@@ -170,6 +171,24 @@ function getWeek (date) {
   // Number of weeks between target Thursday and first Thursday
   var weekDiff = (targetThursday - firstThursday) / (86400000 * 7);
   return 1 + Math.floor(weekDiff);
+  */
+  
+  if (!currentDate || !(currentDate instanceof Date)) {
+    return 0;
+  }
+
+  const date = new Date(currentDate.getTime());
+  date.setHours(0, 0, 0, 0);
+
+  date.setDate(date.getDate() + 3 - ((date.getDay() + 6) % 7));
+
+  const firstWeek = new Date(date.getFullYear(), 0, 4);
+  const MILLISECONDS_IN_DAY = 86400000; // 24 * 60 * 60 * 1000
+
+  const currentYearDay = (date.getTime() - firstWeek.getTime()) / MILLISECONDS_IN_DAY;
+
+  return 1 + Math.round((currentYearDay - 3 + ((firstWeek.getDay() + 6) % 7)) / 7);
+
 }
 
 /**

From 6be331b09fc4e9992c6cd746be5c4d4ed8b53749 Mon Sep 17 00:00:00 2001
From: martakostova <mkostova@camplight.net>
Date: Fri, 18 Mar 2022 22:00:02 +0500
Subject: [PATCH 2/2] update getWeek to support different firstDay of week

---
 src/components/Calendar.vue        |  2 +-
 src/components/date_util/native.js |  4 +--
 src/components/dateformat.js       | 43 +++++++++++-------------------
 3 files changed, 18 insertions(+), 31 deletions(-)

diff --git a/src/components/Calendar.vue b/src/components/Calendar.vue
index 49b9f1bb..cba93261 100644
--- a/src/components/Calendar.vue
+++ b/src/components/Calendar.vue
@@ -29,7 +29,7 @@
       :key="index"
     >
       <td v-if="showWeekNumbers && (index%7 || index===0)" class="week">
-        {{ $dateUtil.weekNumber(dateRow[0]) }}
+        {{ $dateUtil.weekNumber(dateRow[0], locale.firstDay) }}
       </td>
       <td
         v-for="(date, idx) in dateRow"
diff --git a/src/components/date_util/native.js b/src/components/date_util/native.js
index a147cade..b9b0907d 100644
--- a/src/components/date_util/native.js
+++ b/src/components/date_util/native.js
@@ -13,8 +13,8 @@ const DateUtil = {
   daysInMonth: (year, month) => {
     return new Date(year, month, 0).getDate()
   },
-  weekNumber: (date) => {
-    return getWeek(date)
+  weekNumber: (date, firstDay) => {
+    return getWeek(date, firstDay)
   },
   format: (date, mask) => {
     return dateFormat(date, mask)
diff --git a/src/components/dateformat.js b/src/components/dateformat.js
index e6fefc66..7068298a 100644
--- a/src/components/dateformat.js
+++ b/src/components/dateformat.js
@@ -150,44 +150,31 @@ function pad (val, len) {
  * @param  {Object} `date`
  * @return {Number}
  */
-function getWeek (currentDate = new Date()) {
-  /*
+function getWeek (date = new Date(), weekstart) {
+  // Set default for weekstart and clamp to useful range
+  if (weekstart === undefined) weekstart = 1; // monday is by default
+  weekstart %= 7;
+
   // Remove time components of date
   var targetThursday = new Date(date.getFullYear(), date.getMonth(), date.getDate());
 
   // Change date to Thursday same week
-  targetThursday.setDate(targetThursday.getDate() - ((targetThursday.getDay() + 6) % 7) + 3);
+  // Replaced offset of (6) with (7 - weekstart)
+  var dayNr = (targetThursday.getDay() + 7 - weekstart) % 7;
+  targetThursday.setDate(targetThursday.getDate() - dayNr + 3);
 
   // Take January 4th as it is always in week 1 (see ISO 8601)
-  var firstThursday = new Date(targetThursday.getFullYear(), 0, 4);
-
-  // Change date to Thursday same week
-  firstThursday.setDate(firstThursday.getDate() - ((firstThursday.getDay() + 6) % 7) + 3);
+  var firstThursday = targetThursday.valueOf();
 
-  // Check if daylight-saving-time-switch occurred and correct for it
-  var ds = targetThursday.getTimezoneOffset() - firstThursday.getTimezoneOffset();
-  targetThursday.setHours(targetThursday.getHours() - ds);
-
-  // Number of weeks between target Thursday and first Thursday
-  var weekDiff = (targetThursday - firstThursday) / (86400000 * 7);
-  return 1 + Math.floor(weekDiff);
-  */
-  
-  if (!currentDate || !(currentDate instanceof Date)) {
-    return 0;
+  targetThursday.setMonth(0, 1);
+  if (targetThursday.getDay() !== 4) {
+      // Change date to Thursday same week
+      targetThursday.setMonth(0, 1 + ((4 - targetThursday.getDay()) + 7) % 7);
   }
 
-  const date = new Date(currentDate.getTime());
-  date.setHours(0, 0, 0, 0);
-
-  date.setDate(date.getDate() + 3 - ((date.getDay() + 6) % 7));
-
-  const firstWeek = new Date(date.getFullYear(), 0, 4);
-  const MILLISECONDS_IN_DAY = 86400000; // 24 * 60 * 60 * 1000
-
-  const currentYearDay = (date.getTime() - firstWeek.getTime()) / MILLISECONDS_IN_DAY;
+  // Number of weeks between target Thursday and first Thursday
 
-  return 1 + Math.round((currentYearDay - 3 + ((firstWeek.getDay() + 6) % 7)) / 7);
+  return 1 + Math.ceil((firstThursday - targetThursday) / 604800000);
 
 }