fn rule_moved(rule: &str, span: Span, zone: &TimeZone) -> Option<String>Expand description
A repeating event’s rule, its occurrences moved by span on the clock: a
weekly rule’s days (BYDAY=MO,WE) move with them, and its end (UNTIL) by as
much. None when the move would not keep what the rule says: days set
otherwise (a day of the month, “the first Monday”) moved to another day,
or hours set in the rule (BYHOUR) moved to another time.