diff --git a/backup.nix b/backup.nix
index 79649a0..4da814e 100644
--- a/backup.nix
+++ b/backup.nix
@@ -86,7 +86,7 @@ in {
       bucket="$(grep 'bucket=' < "${backupConfigFile}" | sed 's/bucket \?= \?//g')"
       prefix="$(grep 'prefix=' < "${backupConfigFile}" | sed 's/prefix \?= \?//g')"
 
-      s3Dir="s3://$bucket/$prefix""misskey-$(date +'%d-%m-%YT%H.%M.%S')"
+      s3Dir="s3://$bucket/$prefix""misskey-$(date +'%Y-%m-%dT%H.%M.%S')"
       echo "Uploading backups to '$s3Dir'"
 
       function upload () {