The maximum self-destruct timer in a Telegram Secret Chat is 1 week. Users can choose a period after which messages disappear following the recipient's viewing of them.
Secret Chats are Telegram's device-specific, end-to-end encrypted conversations. Unlike ordinary cloud chats, they are not designed to synchronize through Telegram's cloud across every device. The self-destruct timer adds another privacy control by instructing both participating devices to delete a message after the selected interval expires.
The countdown does not normally begin merely when the message is sent. Telegram's documentation explains that it starts when the message is displayed to the recipient, indicated by the message being read. This detail is why the feature is different from a simple scheduled deletion system.
One common mistake is to apply the Secret Chat timer choices to ordinary chats. Telegram also supports automatic deletion in regular chats, but those settings and available intervals are distinct. In a Secret Chat, the longest documented self-destruct interval is one week—not one month, one day, or one hour.