function [st_time, end_time]=chk_time(fname)
%chk_time: returns start and end times of a netCDF file as strings
%
% usage:  [st_time, end_time]=chk_time(fname)
%  outputs: strings of start and end times of the time variables
%  input: filename

%%% START USGS BOILERPLATE -------------
% These programs are intened for us in adjusting metadata terms in 
% netCDF files from the USGS CMGP Oceanographic time-series data 
% archive
%
% Program written Matlab 7.6.0.342 (R2008a)
% Program ran on Linux PC with RHEL4 and on Windows XP PC.
%
% "Although this program has been used by the USGS, no warranty, 
% expressed or implied, is made by the USGS or the United States 
% Government as to the accuracy and functioning of the program 
% and related program material nor shall the fact of distribution 
% constitute any such warranty, and no responsibility is assumed 
% by the USGS in connection therewith."
%%% END USGS BOILERPLATE --------------

if nargin ~= 1; help (mfilename); return; end

%open the netcdf file
eval(['nc=netcdf(''' fname ''');'])
%
%  extract and save the time words in a sensible format
%    time is days, time2 is miliseconds
st_time=gregorian(nc{'time'}(1)+(nc{'time2'}(1)/3600/1000/24));
end_time=gregorian(nc{'time'}(end)+(nc{'time2'}(end)/3600/1000/24));
tt=nc{'time'}(:)+(nc{'time2'}(:)/3600/1000/24);
%disp(['Attribute start, stop are : ' nc.start_time(:) ' - ' nc.stop_time(:)])
dtime=nc.DELTA_T(:);
close(nc)
%figure 
%plot(diff(tt),'.');
%yl=get(gca,'YLim');
%offs=(yl(2)-yl(1))/10;
%text(100,yl(1)+offs,['Mean difference in times is ' num2str(mean(diff(tt)).*86400) ' seconds'])
%title(fname)
 %disp(['Data start, end times are ; ' datestr(st_time) ' - ' datestr(end_time)])
 %disp(['DELTA_T attribute is: ' num2str(dtime)])
 
 % now make sure they match
 st_dif=(datenum(nc.start_time(:))+1721059-(nc{'time'}(1)+(nc{'time2'}(1)/3600/1000/24)))
 if st_dif > .0001
     disp (['start times not equal!'])
 end