Index: openacs-4/packages/acs-subsite/www/resources/core.js
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/acs-subsite/www/resources/core.js,v
diff -u -r1.17.2.4 -r1.17.2.5
--- openacs-4/packages/acs-subsite/www/resources/core.js	20 Aug 2020 14:11:51 -0000	1.17.2.4
+++ openacs-4/packages/acs-subsite/www/resources/core.js	8 Oct 2022 19:50:02 -0000	1.17.2.5
@@ -289,8 +289,7 @@
 Calendar._C = null;
 
 /// detect a special case of "web browser"
-Calendar.is_ie = ( /msie/i.test(navigator.userAgent) &&
-                   !/opera/i.test(navigator.userAgent) );
+Calendar.is_ie = (window.document.documentMode);
 
 // short day names array (initialized at first constructor call)
 Calendar._DN3 = null;