--- a/extra/ncArray/inst/nctimeunits.m	Mon Apr 06 18:44:52 2015 +0000
+++ b/extra/ncArray/inst/nctimeunits.m	Thu Apr 09 10:02:47 2015 +0000
@@ -5,31 +5,61 @@
 % Parse the netCDF time unit u and returns the time offset (days since 31 
 % December 1 BC, as datenum) and scaling factor f (in days).
 % See the netCDF CF convention for the structure of the time units.
+% http://cfconventions.org/Data/cf-conventions/cf-conventions-1.6/build/cf-conventions.html#time-coordinate
+% Also: http://www.unidata.ucar.edu/software/thredds/current/netcdf-java/CDM/CalendarDateTime.html
 
 function [t0,f] = nctimeunits(u)
 
-if strfind(u,'seconds')
+% years in days for udunits
+% http://cfconventions.org/Data/cf-conventions/cf-conventions-1.6/build/cf-conventions.html#time-coordinate
+year_in_days =  365.242198781;
+
+
+l = strfind(u,'since');
+
+if length(l) ~= 1
+    error(['time units sould expect one "since": "' u '"']);
+end
+
+period = strtrim(lower(u(1:l-1)));
+reference_date = strtrim(u(l+6:end));
+
+if strcmp(period,'millisec') || strcmp(period,'msec')
+  f = 1/(24*60*60*1000);
+elseif strcmp(period,'second') || strcmp(period,'seconds') ...
+   || strcmp(period,'s') || strcmp(period,'sec')
   f = 1/(24*60*60);
-elseif strfind(u,'hours')
+elseif strcmp(period,'minute') || strcmp(period,'minutes') ...
+       || strcmp(period,'min')
+  f = 1/(24*60);
+elseif strcmp(period,'hour') || strcmp(period,'hours') ...
+       || strcmp(period,'hr')
   f = 1/24;
-elseif strfind(u,'days')
+elseif strcmp(period,'day') || strcmp(period,'days')
   f = 1;
+elseif strcmp(period,'week') || strcmp(period,'weeks')
+  f = 1/(24*60*60*7);
+elseif strcmp(period,'year') || strcmp(period,'years') ...
+       strcmp(period,'yr')
+  f = year_in_days;
+elseif strcmp(period,'month') || strcmp(period,'months') ...
+       strcmp(period,'mon')
+  f = year_in_days/12;
 else
-  error(['unknown units "' u '"']);
+  error(['unknown units "' period '"']);
 end
   
-l = strfind(u,'since')+6;
 
 try
-  t0 = datenum(u(l:end),'yyyy-mm-dd HH:MM:SS');
+  t0 = datenum(reference_date,'yyyy-mm-dd HH:MM:SS');
 catch
   try
-    t0 = datenum(u(l:end),'yyyy-mm-ddTHH:MM:SS');
+    t0 = datenum(reference_date,'yyyy-mm-ddTHH:MM:SS');
   catch    
     try
-      t0 = datenum(u(l:end),'yyyy-mm-dd');
+      t0 = datenum(reference_date,'yyyy-mm-dd');
     catch
-      error(['date format is not recogized ' u(l:end)])
+      error(['date format is not recogized ' reference_date])
     end
   end
 end