diff --git a/help b/help
index dd08080..d927420 100755
--- a/help
+++ b/help
@@ -6,7 +6,7 @@ echo "  $ new <name>                         create new repository"
 echo "  $ mirror <url> [name]                mirror remote repository"
 echo "  $ upstream <repo> <url>              set repository to push to a given remote"
 echo "  $ downstream <repo> <url>            set repository to fetch from a given remote"
-echo "  $ sync                               push and pull all mirrored repositories"
+echo "  $ fetch-mirrors                      push and pull all mirrored repositories"
 echo "  $ tree <repo>                        show file tree of repo at HEAD"
 echo "  $ log <repo>                         show commit log of repo"
 echo "  $ head <repo> <name>                 change default branch of repository"
@@ -15,5 +15,6 @@ echo "  $ owner <repo> [owner]               set or unset owner for repository"
 echo "  $ group <repo> [group]               set or unset group for repository"
 echo "  $ page <repo> [page]                 set or unset homepage for repository"
 echo "  $ pic <repo> [href]                  set or unset picture url for repository"
+echo "  $ update-time                        force update idle times for all repos"
 echo "  $ show <repo>                        make repository public"
 echo "  $ hide <repo>                        hide public repository"
diff --git a/update-time b/update-time
new file mode 100755
index 0000000..0c1f6c7
--- /dev/null
+++ b/update-time
@@ -0,0 +1,30 @@
+#!/usr/bin/env python3
+
+import os
+import subprocess
+from pathlib import Path
+
+GIT_ROOT = Path(os.environ.get("GIT_ROOT_DIR") or "/srv/git/")
+
+def update_time(repo: Path) -> str:
+	cmd = ["git", "for-each-ref", "--sort=-authordate", "--count=1", "--format='%(authordate:iso8601)'" ]
+	proc = subprocess.run(cmd, cwd=repo, stdout=subprocess.PIPE)
+	time = proc.stdout.decode().strip()
+	with open(repo / "info" / "web" / "last-modified", "w") as f:
+		f.write(time)
+	return time
+
+def run_on_all_repos(root: Path):
+	for element in os.listdir(root):
+		full_path = root / element
+		if element.startswith("."):
+			pass # ignore hidden files
+		elif element.endswith(".git"):
+			time = update_time(full_path)
+			print(f"last update for '{element.replace('.git','')}': {time}")
+		elif os.path.isdir(root / element):
+			run_on_all_repos(root / element)
+
+if __name__ == "__main__":
+	run_on_all_repos(GIT_ROOT)
+