DateTimeToTimeZone with Invalid Timezone

I've been working on a PeopleCode App Class API for creating iCalendar files. To convert from an event's time zone to the iCalendar UTC format, I've been using the PeopleCode DateTimeToTimeZone function. I was curious what would happen if I used an invalid time zone value for the source time zone parameter. I thought the function would throw an error. Instead, the function performs the conversion, but uses the base time zone as the source time zone. The function will also use the base time zone if you pass in an invalid time zone for the destination time zone. In fact, if you pass in an invalid time zone for both the source and destination time zone, then this function will not perform a conversion. Instead, it will return the same value as the OldDateTime parameter.

Since it is Summer, I thought I would try passing PDT and EDT. Of course, I expected a 3 hour difference between the 2 time zones. I was shocked to see the same results for both time zones. It was this test that clued me in to this base time zone behavior. Just to confirm, I tried JJM, 123456, PST, EST, and EET. JJM, 123456, and PST all returned the same result, the base time zone value (PST is my base time zone). EST and EET returned the expected values corresponding to those time zones.

Just in case you are working on your own ics calendar integration and are wondering how to format dates, here is the code I'm using:

Function formatDateTimeToUTC (&dttm as DateTime, &timezone as String) Returns String
   Local datetime &tempTime = DateTimeToTimeZone(&dttm, &timezone, "UTC");

   Return Year(&tempTime) | NumberToDisplayString("%02", Month(&tempTime)) | NumberToDisplayString("%02", Day(&tempTime)) | "T" | NumberToDisplayString("%02", Hour(&tempTime)) | NumberToDisplayString("%02", Minute(&tempTime)) | NumberToDisplayString("%02", Second(&tempTime)) | "Z";
End-Function;