I process the NYT portion of the English Gigaword Corpus with Stanford CoreNLP. While it is still on-going the following message is logged several times:
Unknown variable: WEEKDAY
"annotators", "tokenize, ssplit, pos, lemma, ner, parse, depparse, mention, coref"
The problem should be resolved with this pull-request: https://github.com/stanfordnlp/CoreNLP/pull/277