35115: Scheduling does not support this timestamp

This error occurs when SendAt falls outside the supported window for a scheduled message. Set SendAt to a UTC ISO-8601 timestamp that is more than 5 minutes (300 seconds) from the request time and no more than 35 days in the future.

• SendAt is less than 5 minutes from when Twilio receives the request.
• SendAt is more than 35 days in the future.
• You created the timestamp too close to the minimum lead time, and application delay pushed it out of range before Twilio received the POST request.
• SendAt is not in the expected YYYY-MM-DDTHH:MM:SSZ format in UTC.

• Update SendAt so it is more than 5 minutes (300 seconds) from the request time and no more than 35 days in the future.
• Send SendAt as a UTC ISO-8601 timestamp in YYYY-MM-DDTHH:MM:SSZ format.
• If you schedule close to the minimum allowed time, add buffer before you send the API request so Twilio receives it within the supported window.

• Message Scheduling
• Messages resource
• Messaging API Overview