[Jim Lester]

Originally Posted by kovidgoyal

According to the following links

if a timezone is omitted it is assumed to be a local time zone

http://www.cl.cam.ac.uk/~mgk25/iso-time.html#zone
http://en.wikipedia.org/wiki/ISO_8601#Times

The spec for W3C dates/datetime gives no such latitude. If you include time you must include timezone.

Valid W3C Formats from http://www.w3.org/TR/NOTE-datetime

Year:
YYYY (eg 1997)
Year and month:
YYYY-MM (eg 1997-07)
Complete date:
YYYY-MM-DD (eg 1997-07-16)
Complete date plus hours and minutes:
YYYY-MM-DDThh:mmTZD (eg 1997-07-16T19:20+01:00)
Complete date plus hours, minutes and seconds:
YYYY-MM-DDThh:mm:ssTZD (eg 1997-07-16T19:20:30+01:00)
Complete date plus hours, minutes, seconds and a decimal fraction of a
second
YYYY-MM-DDThh:mm:ss.sTZD (eg 1997-07-16T19:20:30.45+01:00)

Besides, whose localtime, the creator's and if so what is the creator's localtime vs the consumer's localtime. For a long lived document, time without timezone is close to useless.