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Re: time unit in CF-netCDF

To be CF compliant, you should write the units in days and use time-bounds to set the edges of the (irregular) intervals. the attribute unit must be in udunits -- P4D is not or P 4 day are not acceptable. 


Benno


Wenli Yang wrote:




Hi,
How to express the unit of an irregular period of time in the time coordinate variable in CF-netCDF? For example, for two 4-day periods: a) between 2007-01-01 and 2007-01-04; and b) between 2007-01-05 to 2007-01-08, which of the followings are correct? 
    1. time(time)=1,2       unit = "P 4 day since 2007-01-01"
    2. time(time)=1,2       unit = "P4D since 2007-01-01"
There are names for regular time periods, such as week and fortnight, in udunits.dat. For irregular time period, such as 3 days 1 hours and 5 minutes, I am not sure if we should use ISO 8601 expression, "P1M3DT1H5M" or something like "P 1 month 3 day 1 hour 5 minute" as unit. 

Thanks.

Wenli
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