This is a regression from the last push for bug 1280898 (occurring for both backends): https://treeherder.mozilla.org/#/jobs?repo=comm-central&revision=2d001923cb988f8f6a7108093f5388e9b627bc01 There is most probably an id change missing: 19:39:01 INFO - PROCESS | 20313 | Error: Couldn't find Unknown/Olson/Timezone 19:39:01 INFO - PROCESS | 20313 | JavaScript error: resource://calendar/modules/calUtils.jsm -> file:///builds/slave/test/build/application/thunderbird/extensions/%7Be2fda1a4-762b-4020-b5ad-a41df1933103%7D/calendar-js/calIcsParser.js, line 242: ReferenceError: dt is not defined 19:39:01 INFO - (xpcshell/head.js) | test run_next_test 2 finished (2) 19:39:01 INFO - Unexpected exception NS_ERROR_XPC_JAVASCRIPT_ERROR_WITH_DETAILS: [JavaScript Error: "dt is not defined" {file: "resource://calendar/modules/calUtils.jsm -> file:///builds/slave/test/build/application/thunderbird/extensions/%7Be2fda1a4-762b-4020-b5ad-a41df1933103%7D/calendar-js/calIcsParser.js" line: 242}]'[JavaScript Error: "dt is not defined" {file: "resource://calendar/modules/calUtils.jsm -> file:///builds/slave/test/build/application/thunderbird/extensions/%7Be2fda1a4-762b-4020-b5ad-a41df1933103%7D/calendar-js/calIcsParser.js" line: 242}]' when calling method: [calIIcsParser::parseString] 19:39:01 INFO - _createDateTime@/builds/slave/test/build/tests/xpcshell/tests/calendar/test/unit/test_gdata_provider.js:608:9 19:39:01 INFO - test_dateToJSON@/builds/slave/test/build/tests/xpcshell/tests/calendar/test/unit/test_gdata_provider.js:648:20 19:39:01 INFO - _run_next_test@/builds/slave/test/build/tests/xpcshell/head.js:1566:9 19:39:01 INFO - do_execute_soon/<.run@/builds/slave/test/build/tests/xpcshell/head.js:713:9 19:39:01 INFO - _do_main@/builds/slave/test/build/tests/xpcshell/head.js:210:5 19:39:01 INFO - _execute_test@/builds/slave/test/build/tests/xpcshell/head.js:545:5 19:39:01 INFO - @-e:1:1 19:39:01 INFO - exiting test

Let's whether the test works with this patch again: https://treeherder.mozilla.org/#/jobs?repo=try-comm-central&revision=fedde1eea6f149d6ddfd39e77fd65efb3ae687e9

Comment on attachment 8792306 [details] [diff] [review] FixLeftoverFromIdChangeInIcsParser-V1.diff Ah yes, I had some conflicts I have improperly resolved here. r=philipp