the ietf meeting parts of upcoming.ics end a day early

[rjsparks]

Our custom ics should take into account (from RFC5545)

The "DTEND" property
for a "VEVENT" calendar component specifies the non-inclusive end
of the event.

See

datatracker/ietf/templates/meeting/upcoming.ics

Line 28 in 287cf0f

DTEND;VALUE=DATE{% if meeting.time_zone %};TZID={{ meeting.time_zone|ics_esc }}{% endif %}:{{ meeting.end_date|date:"Ymd" }}