Renders start–end; when both fall on the same day (per isSameDay), the end's date is omitted (only its time is shown). includeDuration appends a formatted duration in parentheses.
Same day, includeDuration=false (default): –
Same day, includeDuration=true: – (2 h 30 min)
Spans midnight, includeDuration=true: – (10 h)
locale="en", same day, includeDuration=true: – (2 h 30 min)
Helpers used directly: isSameDay(start, end) for the same day range above is true; formatDuration(start, end) gives "2 h 30 min"; and formatDurationMinutes(135) gives "2 h 15 min".