Actually, I just found this in the [ISO 8601 standard](http://tools.ietf.org/html/rfc3339):

>  Timestamps can express times that occurred before the introduction
>  of UTC.  Such timestamps are expressed relative to universal time,
>  using the best available practice at the stated time.

Which in this case, will always be UTC, so we're safe. I can add a note to the docs clarifying this. I'll also make sure this is noted in the TimeZones.jl package, using the "best available practice" for the timezones that provide that information.