Sorry, no, ISO 8601 (and thus EDTF) does not support the specification of a time zone without a time.
I can see the use case for it, but I would imagine that the original developers of 8601 would explain that the time zone is an offset, specifically an offset applied to the time, and if it could be supplied for a date it would suffer from semantic ambiguity. I think they would suggest that the location of the event be supplied in a separate data element.
> -----Original Message-----
> From: Discussion of the Developing Date/Time Standards
> [mailto:[log in to unmask]] On Behalf Of GERRY ASHTON
> Sent: Saturday, August 05, 2017 1:54 PM
> To: [log in to unmask]
> Subject: [DATETIME] Combining time zone with day precision
> It is not clear to me if ISO 8601-2004 (and hence, the lowest level of EDTF)
> provides for a way to express that a date/time with day precision (e.g. 2017-08-
> 05) is known to be in a particular time zone (e.g. -04:00) without resorting to
> ranges. It seems to me this would occur very often, were a source only gives
> the date of an event, but the time zone in which the event can be firmly
> For example, would 2017-08-05T-04:00 be valid?
> I exclude ranges because many profiles of ISO-8601 do not support ranges.
> Gerard Ashton