diff --git a/opencloudComLibrary/src/main/java/eu/opencloud/android/lib/resources/shares/CreateRemoteShareOperation.kt b/opencloudComLibrary/src/main/java/eu/opencloud/android/lib/resources/shares/CreateRemoteShareOperation.kt
index 5dcb5d59f..75a63bc49 100644
--- a/opencloudComLibrary/src/main/java/eu/opencloud/android/lib/resources/shares/CreateRemoteShareOperation.kt
+++ b/opencloudComLibrary/src/main/java/eu/opencloud/android/lib/resources/shares/CreateRemoteShareOperation.kt
@@ -137,7 +137,9 @@ class CreateRemoteShareOperation(
         }
 
         if (expirationDateInMillis > INIT_EXPIRATION_DATE_IN_MILLIS) {
-            val dateFormat = SimpleDateFormat(FORMAT_EXPIRATION_DATE, Locale.getDefault())
+            val dateFormat = SimpleDateFormat(FORMAT_EXPIRATION_DATE, Locale.getDefault()).apply {
+                timeZone = java.util.TimeZone.getTimeZone("UTC")
+            }
             val expirationDate = Calendar.getInstance()
             expirationDate.timeInMillis = expirationDateInMillis
             val formattedExpirationDate = dateFormat.format(expirationDate.time)
@@ -197,6 +199,9 @@ class CreateRemoteShareOperation(
         private const val PARAM_PERMISSIONS = "permissions"
 
         //Arguments - constant values
-        private const val FORMAT_EXPIRATION_DATE = "yyyy-MM-dd"
+        // ISO-8601 UTC format is required by the backend to correctly parse expiration dates,
+        // especially for private user/group share creations and updates, ensuring compatibility
+        // when these features are eventually exposed in the mobile UI.
+        private const val FORMAT_EXPIRATION_DATE = "yyyy-MM-dd'T'HH:mm:ss'Z'"
     }
 }
diff --git a/opencloudComLibrary/src/main/java/eu/opencloud/android/lib/resources/shares/UpdateRemoteShareOperation.kt b/opencloudComLibrary/src/main/java/eu/opencloud/android/lib/resources/shares/UpdateRemoteShareOperation.kt
index 3834d9353..62e5a2bf5 100644
--- a/opencloudComLibrary/src/main/java/eu/opencloud/android/lib/resources/shares/UpdateRemoteShareOperation.kt
+++ b/opencloudComLibrary/src/main/java/eu/opencloud/android/lib/resources/shares/UpdateRemoteShareOperation.kt
@@ -159,7 +159,9 @@ class UpdateRemoteShareOperation
 
         } else if (expirationDateInMillis > INITIAL_EXPIRATION_DATE_IN_MILLIS) {
             // set expiration date
-            val dateFormat = SimpleDateFormat(FORMAT_EXPIRATION_DATE, Locale.getDefault())
+            val dateFormat = SimpleDateFormat(FORMAT_EXPIRATION_DATE, Locale.getDefault()).apply {
+                timeZone = java.util.TimeZone.getTimeZone("UTC")
+            }
             val expirationDate = Calendar.getInstance()
             expirationDate.timeInMillis = expirationDateInMillis
             val formattedExpirationDate = dateFormat.format(expirationDate.time)
@@ -216,7 +218,10 @@ class UpdateRemoteShareOperation
         private const val PARAM_PERMISSIONS = "permissions"
 
         //Arguments - constant values
-        private const val FORMAT_EXPIRATION_DATE = "yyyy-MM-dd"
+        // ISO-8601 UTC format is required by the backend to correctly parse expiration dates,
+        // especially for private user/group share creations and updates, ensuring compatibility
+        // when these features are eventually exposed in the mobile UI.
+        private const val FORMAT_EXPIRATION_DATE = "yyyy-MM-dd'T'HH:mm:ss'Z'"
         private const val INITIAL_EXPIRATION_DATE_IN_MILLIS: Long = 0
     }
 }