diff --git a/resources/assets/javascripts/lib/fullcalendar.js b/resources/assets/javascripts/lib/fullcalendar.js
index b3eb9d1a7d780dd533d534279fb217020eac2756..aebcfaee4d2b7867c2ddda10e7375298c665d29b 100644
--- a/resources/assets/javascripts/lib/fullcalendar.js
+++ b/resources/assets/javascripts/lib/fullcalendar.js
@@ -355,6 +355,9 @@ class Fullcalendar
             },
             minTime: '08:00:00',
             maxTime: '20:00:00',
+            validRange: {
+                start: '1970-01-01'
+            },
             height: 'auto',
             contentHeight: 'auto',
             firstDay: 1,
diff --git a/resources/assets/javascripts/studip-ui.js b/resources/assets/javascripts/studip-ui.js
index 2ef3a6e21a8eb6e346c720a992b91ab492d18d98..967f2d2f016337a684acb9362aef6e25cc2fe107 100644
--- a/resources/assets/javascripts/studip-ui.js
+++ b/resources/assets/javascripts/studip-ui.js
@@ -578,7 +578,8 @@ import eventBus from "./lib/event-bus.ts";
             if (value !== instance.lastVal) {
                 $(this).change();
             }
-        }
+        },
+        minDate: new Date(1970, 0)
     };
 
     $.datepicker.setDefaults({