diff --git a/scripts/cut_off_nightly_beta.py b/scripts/cut_off_nightly_beta.py
new file mode 100755
index 00000000..50c72ee0
--- /dev/null
+++ b/scripts/cut_off_nightly_beta.py
@@ -0,0 +1,45 @@
+#!/usr/bin/env nix-shell
+#!nix-shell -i python3 -p "python3.withPackages (ps: with ps; [ toml requests ])"
+from typing import Callable
+from fetch import update_nightly_index, update_beta_index
+from pathlib import Path
+import re
+import sys
+
+CHANNELS: list[tuple[Path, Callable[[], None]]] = [
+    (Path('manifests/nightly'), update_nightly_index),
+    (Path('manifests/beta'), update_beta_index),
+]
+RE_LATEST_DATE = re.compile('latest = "(.*?)"')
+
+def main():
+    args = sys.argv[1:]
+    if len(args) != 1:
+        print('''
+Usage:
+    {0} <year>
+        Delete all nightly and beta manifests before (excluding) <year>.
+''')
+        exit(1)
+
+    cut_year = int(args[0])
+    for (channel_root, update_index) in CHANNELS:
+        for year_dir in channel_root.iterdir():
+            if year_dir.is_dir() and int(year_dir.name) < cut_year:
+                print(f'deleting {year_dir}')
+                for ver in year_dir.iterdir():
+                    ver.unlink()
+                year_dir.rmdir()
+        def latest_ver():
+            src = (channel_root / 'default.nix').read_text()
+            m = RE_LATEST_DATE.search(src)
+            assert m is not None, f'No latest version:\n{src}'
+            return m[1]
+        before_latest =  latest_ver()
+        update_index()
+        after_latest =  latest_ver()
+        assert before_latest == after_latest, \
+            f'Latest version must not be affected: {before_latest} -> {after_latest}'
+
+if __name__ == '__main__':
+    main()