2.1.8 sent-time Field

The sent-time field is optional. If this field is present, it contains the sent-time-string field, which contains a string that indicates the date and time, in Coordinated Universal Time (UTC), that the original message was sent. The exact format of the string contained in the sent-time-string field is left to the implementation.

The sent-time field can begin with either "SentUtc" or "Sent".<3> The meaning is the same regardless of which string is used.