I agree, except that long years experience in the field of computer security has taught me that what the organizer may consider “local” is profoundly ambiguous. All too often it is just plain wrong. In the case I noted, the organizer was just plain wrong: she explicitly stated “GMT” but meant “BST”.
There are other considerations. For example, the term “EST” is ambiguous, By and large it means UTC-5 but is very frequently interpreted as UTC+10 in Australia.
That is why CERTs are very strongly advised to use UTC and ISO-standard date formats in their communications.