diff --git a/.pnp.cjs b/.pnp.cjs
index 82409e51c..5fcce34d2 100644
--- a/.pnp.cjs
+++ b/.pnp.cjs
@@ -68,7 +68,7 @@ function $$SETUP_STATE(hydrateRuntimeState, basePath) {
             ["file-saver", "npm:2.0.5"],\
             ["highcharts", "npm:11.4.0"],\
             ["html-validate", "virtual:dc3fc578bfa5e06182a4d2be39ede0bc5b74940b1ffe0d70c26892ab140a4699787750fba175dc306292e80b4aa2c8c5f68c2a821e69b2c37e360c0dff36ff66#npm:8.18.1"],\
-            ["ical.js", "npm:2.0.0"],\
+            ["ical.js", "npm:1.5.0"],\
             ["jquery", "npm:3.7.1"],\
             ["jquery-migrate", "virtual:dc3fc578bfa5e06182a4d2be39ede0bc5b74940b1ffe0d70c26892ab140a4699787750fba175dc306292e80b4aa2c8c5f68c2a821e69b2c37e360c0dff36ff66#npm:3.4.1"],\
             ["js-cookie", "npm:3.0.5"],\
@@ -626,7 +626,7 @@ function $$SETUP_STATE(hydrateRuntimeState, basePath) {
             ["@fullcalendar/core", "npm:6.1.11"],\
             ["@types/fullcalendar__core", null],\
             ["@types/ical.js", null],\
-            ["ical.js", "npm:2.0.0"]\
+            ["ical.js", "npm:1.5.0"]\
           ],\
           "packagePeers": [\
             "@fullcalendar/core",\
@@ -5996,10 +5996,10 @@ function $$SETUP_STATE(hydrateRuntimeState, basePath) {
         }]\
       ]],\
       ["ical.js", [\
-        ["npm:2.0.0", {\
-          "packageLocation": "./.yarn/cache/ical.js-npm-2.0.0-00c3a15280-e4a5cf06d2.zip/node_modules/ical.js/",\
+        ["npm:1.5.0", {\
+          "packageLocation": "./.yarn/cache/ical.js-npm-1.5.0-5ba1c69420-51df7a01f4.zip/node_modules/ical.js/",\
           "packageDependencies": [\
-            ["ical.js", "npm:2.0.0"]\
+            ["ical.js", "npm:1.5.0"]\
           ],\
           "linkType": "HARD"\
         }]\
@@ -8352,7 +8352,7 @@ function $$SETUP_STATE(hydrateRuntimeState, basePath) {
             ["file-saver", "npm:2.0.5"],\
             ["highcharts", "npm:11.4.0"],\
             ["html-validate", "virtual:dc3fc578bfa5e06182a4d2be39ede0bc5b74940b1ffe0d70c26892ab140a4699787750fba175dc306292e80b4aa2c8c5f68c2a821e69b2c37e360c0dff36ff66#npm:8.18.1"],\
-            ["ical.js", "npm:2.0.0"],\
+            ["ical.js", "npm:1.5.0"],\
             ["jquery", "npm:3.7.1"],\
             ["jquery-migrate", "virtual:dc3fc578bfa5e06182a4d2be39ede0bc5b74940b1ffe0d70c26892ab140a4699787750fba175dc306292e80b4aa2c8c5f68c2a821e69b2c37e360c0dff36ff66#npm:3.4.1"],\
             ["js-cookie", "npm:3.0.5"],\
diff --git a/.yarn/cache/ical.js-npm-1.5.0-5ba1c69420-51df7a01f4.zip b/.yarn/cache/ical.js-npm-1.5.0-5ba1c69420-51df7a01f4.zip
new file mode 100644
index 000000000..7aa64acf0
Binary files /dev/null and b/.yarn/cache/ical.js-npm-1.5.0-5ba1c69420-51df7a01f4.zip differ
diff --git a/.yarn/cache/ical.js-npm-2.0.0-00c3a15280-e4a5cf06d2.zip b/.yarn/cache/ical.js-npm-2.0.0-00c3a15280-e4a5cf06d2.zip
deleted file mode 100644
index 78ad9f21a..000000000
Binary files a/.yarn/cache/ical.js-npm-2.0.0-00c3a15280-e4a5cf06d2.zip and /dev/null differ
diff --git a/package.json b/package.json
index 1c9f861d6..afcabd13e 100644
--- a/package.json
+++ b/package.json
@@ -25,7 +25,7 @@
     "d3": "7.9.0",
     "file-saver": "2.0.5",
     "highcharts": "11.4.0",
-    "ical.js": "2.0.0",
+    "ical.js": "1.5.0",
     "jquery": "3.7.1",
     "js-cookie": "3.0.5",
     "list.js": "2.3.1",
diff --git a/yarn.lock b/yarn.lock
index 5d2ff5f69..54768ac39 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -4849,10 +4849,10 @@ browserlist@latest:
   languageName: node
   linkType: hard
 
-"ical.js@npm:2.0.0":
-  version: 2.0.0
-  resolution: "ical.js@npm:2.0.0"
-  checksum: e4a5cf06d264fd09fa30fd54ae78530c899ce605547c9ac68264c1b2302c1c4522956a19f265b33ffbb21ca500f7938f6c774f1abcd147ee6b90dd91c090719f
+"ical.js@npm:1.5.0":
+  version: 1.5.0
+  resolution: "ical.js@npm:1.5.0"
+  checksum: 51df7a01f462dc8a02b3c3c28acb288756071044c4a8b56ff5179995bb219e569e72cfedac6f4ab03dc643be34f5d88c09a7d79c4be6ba8a7623b7336eecb110
   languageName: node
   linkType: hard
 
@@ -7056,7 +7056,7 @@ browserlist@latest:
     file-saver: 2.0.5
     highcharts: 11.4.0
     html-validate: 8.18.1
-    ical.js: 2.0.0
+    ical.js: 1.5.0
     jquery: 3.7.1
     jquery-migrate: 3.4.1
     js-cookie: 3.0.5