type: string
description: >-
  A timestamp in ISO 8601 format which specifies a date after the current time
  and up to 180 days in the future to send the letter off for production.
  Setting a send date overrides the default [cancellation window](#section/Cancellation-Windows)
  applied to the mailpiece. Until the `send_date` has passed, the mailpiece can be canceled. If a date
  in the format `2017-11-01` is passed, it will evaluate to midnight UTC of that date (`2017-11-01T00:00:00.000Z`).
  If a datetime is passed, that exact time will be used. A `send_date` passed with no time zone will default to UTC,
  while a `send_date` passed with a time zone will be converted to UTC.
anyOf:
  - format: date-time
  - format: date