From c14e1712ea7e42bdb7b2d246a9fcad3ca81aa048 Mon Sep 17 00:00:00 2001
From: Ivan Trusov <i.l.trusov@gmail.com>
Date: Fri, 13 May 2022 11:00:36 +0300
Subject: [PATCH 1/2] Fix basedate calculation

Correct numdate / datenum calculation to eliminate problems
with timezones that equal nowadays but were different
in the past (e.g. Europe/Minsk and Europe/Moscow)
---
 xlsx.js | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/xlsx.js b/xlsx.js
index 5cc5758..45b1a0e 100644
--- a/xlsx.js
+++ b/xlsx.js
@@ -3214,16 +3214,19 @@ function evert_arr(obj) {
 	return o;
 }
 
-var basedate = new Date(1899, 11, 30, 0, 0, 0); // 2209161600000
+var basedate = new Date(); // 2209161600000
+basedate.setUTCFullYear(1899, 11, 30);
+basedate.setUTCHours(0, 0, 0);
+
 function datenum(v, date1904) {
 	var epoch = v.getTime();
 	if(date1904) epoch -= 1462*24*60*60*1000;
-	var dnthresh = basedate.getTime() + (v.getTimezoneOffset() - basedate.getTimezoneOffset()) * 60000;
+	var dnthresh = basedate.getTime() + v.getTimezoneOffset() * 60000;
 	return (epoch - dnthresh) / (24 * 60 * 60 * 1000);
 }
 var refdate = new Date();
-var dnthresh = basedate.getTime() + (refdate.getTimezoneOffset() - basedate.getTimezoneOffset()) * 60000;
 var refoffset = refdate.getTimezoneOffset();
+var dnthresh = basedate.getTime() + refoffset * 60000;
 function numdate(v) {
 	var out = new Date();
 	out.setTime(v * 24 * 60 * 60 * 1000 + dnthresh);

From 1dfabe74b1403d2dc48729103afb2b9dd2df28fd Mon Sep 17 00:00:00 2001
From: Ivan Trusov <i.l.trusov@gmail.com>
Date: Tue, 31 May 2022 17:26:54 +0300
Subject: [PATCH 2/2] Fix basedate calculation
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Philippe Rivière <fil@rezo.net>
---
 xlsx.js | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/xlsx.js b/xlsx.js
index 45b1a0e..c83e754 100644
--- a/xlsx.js
+++ b/xlsx.js
@@ -3214,9 +3214,7 @@ function evert_arr(obj) {
 	return o;
 }
 
-var basedate = new Date(); // 2209161600000
-basedate.setUTCFullYear(1899, 11, 30);
-basedate.setUTCHours(0, 0, 0);
+var basedate = new Date(Date.UTC(1899, 11, 30, 0, 0, 0)); // 2209161600000
 
 function datenum(v, date1904) {
 	var epoch = v.getTime();