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iCalendar Timezone Problems and Recommendations
2. Identified implementation problems and recommendations
2.1. General time zone issues
2.1.1.Clause2.1.1How should a client / server react towards existing meetings when a time zone rule changes? For example, if DST changes for a time zone, should the existing meetings created in that time zone be adjusted to the new rules or should they remain the same and let the changes be applied only to newly created events?

2.1.1.1.

In most cases, meetings created using a time zone should use the new time zone definition so that effected recurrences reflect the time zone change (Example: Lunch at noon every day). Cases where the timing has to be fixed should be created in UTC (Example: Enter a few digits on a terminal every 108 minutes), which has no dependency on time zone rules.