DUE was read only when a VTODO had no DTSTART, and never as the end. A task
carrying both imported as a zero-length event instead of the span between them.
It is now resolved after the property sweep, so a DUE ahead of the DTSTART isn't
mistaken for the start either.
A timed VALARM firing after the start is a follow-up alarm and models no lead
time — clamping it to zero invented a reminder at the start that the file never
asked for. Dropped again, as the insert path did before. The clamp stays for
all-day, where it's how the Fossify family writes "on the day at 09:00".
Jean-Luc Makiola
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