sdfwrite and sdfattr

Jennifer Adams jma at COLA.IGES.ORG
Thu Feb 26 10:06:35 EST 2009

That's a bug that was fixed in 2.0.a5.

The correct way to write the time axis units is:
"minutes since yyyy-mm-dd hh:min"


On Feb 26, 2009, at 9:57 AM, Steven C Chan wrote:

> Hello everyone,
> The version of Grads involved is 2.0a3.
> I am trying out the new netCDF routines for Grads, and I am having
> some
> issues with how units of time is generated when sdfwrite and inability
> to manually corrected the problem using sdfattr.
> When the first sdfwrite command is used like: sdfwrite
> precipitation. It
> generates a new netCDF file with the variable precipitation with also
> the time defined with it, but the units of time is always defined like
> "minutes since dd-mm-yyyy hr:min".

> It seemed Grads itself using sdfopen does not like time to be defined
> that way; sdfopen likes "minutes since yyyy-mm-dd hr:min" (as
> correctly
> stated in COARDS standard). When the incorrectly time unit defined .nc
> file is opened with sdfopen, Grads will try to read it as yyyy-mm-dd.
> For example:
> "Minutes since 1-1-1948 00:00" as generated by sdfwrite will become:
> 01:01:19 00:00 with sdfopen (the 48 from 1948 is dropped as there is
> obviously no day 1948 in any calender month.
> Using sdfattr trying to override the units of time does not work; it
> just simply will not allow me to do it.
> Is this a known issue with sdfwrite / sdfattr?
> Thanks
> Steven Chan

Jennifer M. Adams
4041 Powder Mill Road, Suite 302
Calverton, MD 20705
jma at

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