Optional DTSTART -> Updates specified in RFC 5545?

[niccokunzmann]

You can read this in the RFC:

; The following is REQUIRED if the component
; appears in an iCalendar object that doesn't
; specify the "METHOD" property; otherwise, it
; is OPTIONAL; in any case, it MUST NOT occur
; more than once.
dtstart

So, I wonder: The start is quite an important property to the event. It might be that the standard defines some way of updating things with 'missing' attributes. I wonder if we can or must consider that for mergecal.