# 35111: SendAt timestamp is missing

Log Type: APPLICATION

Log Level: ERROR

## Description

This error occurs when you try to create a scheduled message with `ScheduleType` set to `fixed` and do not include `SendAt`. Scheduled messages require both parameters, and `SendAt` must be a timestamp in ISO-8601 format.

### Possible causes

* You set `ScheduleType` to `fixed` but left out `SendAt`.
* You tried to schedule a message without providing the send time Twilio needs to create the scheduled `Message` resource.

### Possible solutions

* Include `SendAt` whenever you set `ScheduleType` to `fixed`. Use an ISO-8601 timestamp.
* Make sure the scheduled send time is between 15 minutes and 35 days from the time Twilio receives the `POST` request.
* Create the message with a `MessagingServiceSid` when you schedule delivery. Without it, Twilio treats the request as non-scheduled.

#### Additional resources

* [Message Scheduling](/docs/messaging/features/message-scheduling)
* [Messaging API Overview](/docs/messaging/api)