Harmonize timestamps of an existing calendar

[marsianer]

I have a calendar that uses different time zones.
For this reason I would like to harmonize all entries to use the same time zone Europe/Berlin.

• Most of them are floating and UTC (Legacy of GMail).
• I want to make sure that the existing entries don't get broken.

Is this coding correct or did I miss something?

CompatibilityHints.setHintEnabled(CompatibilityHints.KEY_RELAXED_PARSING, true);
for (CalendarComponent calendarComponent : getCalendar().getComponents()) {
    // Start date
    Property dtstartProperty = calendarComponent.getProperty(Property.DTSTART);
    if (dtstartProperty != null) {
        DtStart startDate = (DtStart) dtstartProperty;
        if (startDate.getDate() instanceof DateTime) {
            startDate.setTimeZone(getDefaultTimeZone());
        }
    }
    // End date
    Property dtendProperty = calendarComponent.getProperty(Property.DTEND);
    if (dtendProperty != null) {
        DtEnd endDate = (DtEnd) dtendProperty;
        if (endDate.getDate() instanceof DateTime) {
            endDate.setTimeZone(getDefaultTimeZone());
        }
    }
    // Due date
    Property dueProperty = calendarComponent.getProperty(Property.DUE);
    if (dueProperty != null) {
        Due dueDate = (Due) dueProperty;
        dueDate.setTimeZone(getDefaultTimeZone());
    }
    // Exclusion date
    Property exdateProperty = calendarComponent.getProperty(Property.EXDATE);
    if (exdateProperty != null) {
        ExDate exclusionDate = (ExDate) exdateProperty;
        exclusionDate.setTimeZone(getDefaultTimeZone());
    }
    // Recurrence date
    Property rdateProperty = calendarComponent.getProperty(Property.RDATE);
    if (rdateProperty != null) {
        RDate recurrenceDate = (RDate) rdateProperty;
        recurrenceDate.setTimeZone(getDefaultTimeZone());
    }
}
// Save to file...

[benfortuna]

First thing that comes to mind is recurrence instances. If you have any recurring events, and have overridden any of them you may have RDATE properties which will also need a TZID reference.

You may want to look at the spec (RFC5545) just to see which properties can have a TZID parameter, and cross-check with your file. It is an interesting project and probably could be made into a general tool for this type of conversion..

[marsianer]

Time Zone Identifier
https://datatracker.ietf.org/doc/html/rfc5545#section-3.2.19

This parameter MUST be specified on

• DTSTART (Start date)
• DTEND (End date)
• DUE (Due date)
• EXDATE (Exclusion date)
• RDATE (Recurrence date)

when either a DATE-TIME or TIME value type is specified and when the value is neither a UTC or a "floating" time.

[marsianer]

Since I set the time zone explicitly on the properties mentioned, do I still need the VTIMEZONE entries?

[benfortuna]

Strictly yes, as the TZID parameter is meant to be a reference to a VTIMEZONE component.

But you may find some implementations will allow you to use well known timezone identifiers without needing to include the VTIMEZONE definition (e.g. Europe/London).

[marsianer]

Thanks for your help.
The harmonization has just been successfully completed.

All events now use the same time zone.