The server autosaves every 5 minutes by default and keeps a rotation of autosaves. NUM_AUTOSAVES in Startup (default 3) sets how many. Raise it to 5-10 if you have the disk space; each late-game save is 20-50 MB.
Change the interval in-game: Server Manager → Server Settings → Autosave interval.
Restoring an autosave
Server Manager → Manage Saves shows every autosave with its timestamp; Load the one from before the mistake.
Panel backups
Autosaves protect against in-game mistakes. A panel backup protects against everything else and lets you move hosts. One nightly backup schedule is enough.