The Schedule-Tag response header provides the current value of the CALDAV:schedule-tag property value. The behavior of this response header is described in Section 3.2.10.
All scheduling object resources MUST support the Schedule-Tag header.
Schedule-Tag = "Schedule-Tag" ":" opaque-tag ; "opaque-tag" is defined in Section 3.11 of [RFC2616].
Example
Schedule-Tag: "12ab34-cd56ef"