How to schedule messages in Messages
You can schedule messages to send on phones with Android 7 and newer. If your phone isn't connected to Wi-Fi or data at the scheduled time, your message will be sent when your device reconnects.
Open the Messages app Android Messages.
Open a conversation.
Enter your message.
Touch and hold Send Send.
Choose from the suggestions.
Optional: If you choose your own date and time, a calendar opens. After you pick a date, a clock opens so you can pick a time. Tap Next.
Tap Send Send.
Tip: If you open a conversation with a scheduled message, there will be a “Scheduled message” notification.