Hi-
Just to follow up on the issue that arose regarding dates.
Last week I said:
I will look into the unit parsing for this case though. I'm
pretty sure that the underlying VisAD unit parsing only handles
UTC, GMT and Z as valid timezones. I'll see if we can ammend that.
The background is that the unit specification:
hours since 2003-12-01 00:00:00MDT
was not taken as a valid unit. In looking at the description of
the ISO spec for time (ISO 8601) found at:
http://www.cl.cam.ac.uk/%7Emgk25/iso-time.html
parsing of a time zone like "MDT" can be problematic. To quote
from that reference:
"There exists no international standard that specifies abbreviations for
civil time zones like CET, EST, etc. and sometimes the same abbreviation
is even used for two very different time zones. In addition, politicians
enjoy modifying the rules for civil time zones, especially for daylight
saving times, every few years, so the only really reliable way of
describing a local time zone is to specify numerically the difference of
local time to UTC".
Given that information, I am not going to make any changes to the
unit parsing to handle time zone specifications other than Z, UTC or
GMT (which the underlying VisAD unit parsing already supports).
As a side note, CF specifies that unit specifications should be udunits
compatible and at first glance udunits gives no error for the unit
specification "hours since 2003-12-01 00:00:00MDT". In this case,
the MDT is ignored, so it takes it as GMT anyway. udunits
does support the +/-hh:mm format and that is what should be used.
Don
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Don Murray UCAR Unidata Program
dmurray@xxxxxxxxxxxxxxxx P.O. Box 3000
(303) 497-8628 Boulder, CO 80307
http://www.unidata.ucar.edu/staff/donm
"Time makes everyone interesting, even YOU!"
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