UTC vs Etc/UTC - CalendarBuilder Exception (java.time.DateTimeException: Unknown timezone identifier [UTC])

[KaiSuchomel]

Describe the bug
When using a Calendar with Timezone UTC and convert to String and back a Exception occurs.
java.time.DateTimeException: Unknown timezone identifier [UTC]
Hint: see TimeZoneRegistryImpl.getZoneId()
The contained zoneIds (Field) does not contain a Value for UTC.

To Reproduce
KaiSuchomel@b812997
I have created a Test(UTCCalendarEqualsTest) with UTC and Etc/UTC Calendars.
The UTC Test is failing with the Exception.

Expected behavior
UTC Test should be handled like Etc/UTC

Environment (please complete the following information):

• OS: MacOs
• Java Version 21
• iCal4j 4.0.0-rc6-pre

[KaiSuchomel]

@ChMThiel FYI

[benfortuna]

UTC is defined as an alias of Etc/UTC, but I think there was an issue with how the aliases are resolved. Have committed a fix now. It's included in release rc6.

[KaiSuchomel]

@benfortuna
My Test is still failing.
See Commit (KaiSuchomel@1220dae) for the Testcase.

[KaiSuchomel]

Please Reopen this Issue. Thx