Open the Telegram app updated to the version 5.11 or higher.
  Enter in the individual or group chat that you want to schedule a message for.
  Write the message and hold down the send button.
  Tap Schedule Message and set a date and time for the content to be sent.
  Tap the lower button to leave the message scheduled. ((https://blog.en.uptodown.com/schedule-messages-telegram-android/))