There are two ways to do this.
(1) Easier
Change the date format in excel itself....
format cells-> select custom --> (type the format you need)
your case dd-mmm-yyyy HH:MM:SS
then read this file
(2) Round about way
lets say your excle file first column contians date in any format and second column contains numbers. Save the file in csv format and use textscan command(i believe you cannot read strings using xlsread command)
fid=fopen('FileName.csv','r');
fileformat='%s %f';
data=textscan(fid,fileformat,'headerlines',2,'delimiter',',');
fclose(fid);
Assuming your first and second rows contain some headings/units 'headerlines',2 will ignore first two rows.
Now 'Data' is a cell data type with Data{1} containing array of date strings
dateformat='dd-mmm-yyyy HH:MM:SS' % Could be any format
%====if you want to plot use
plot(Data{1},Data{2})
datetick(dateformat) % Will put your dates in required format on axis
% ==if you want to rewire formatted strings to excel file==
ReqDates=datestr(datenum(Data{1}),dateformat)
ReqDates will contain a string of dates in required format
you can drirectly write/overwrite these dates to you excel file using xlswrite('Filename.xls',ReqDates,'Worksheet','Range');
Hope this helps.
Nodal DOF