Fix typo

hardware-configuration.nix

@@ -22,7 +22,7 @@
         mount /dev/disk/by-partlabel/disk-stationette-root /btrfs_tmp
         if [[ -e /btrfs_tmp/root ]]; then
             mkdir -p /btrfs_tmp/old_roots
-            timestamp=$(dat +%Y-%m-%d_%H-%M-%S)
+            timestamp=$(date +%Y-%m-%d_%H-%M-%S)
             mv /btrfs_tmp/root "/btrfs_tmp/old_roots/$timestamp"
         fi
 
@@ -34,7 +34,7 @@
             btrfs subvolume delete "$1"
         }
 
-        for i in $(find /btrfs_tmp/old_roots/ -maxdepth 1 -mtime +30); do
+        for i in $(find /btrfs_tmp/old_roots/ -maxdepth 1 -mtime +7); do
             delete_subvolume_recursively "$i"
         done