Converting time/dates to hours or number

Hi I'm getting difficult to convert time dates to hours so i can set paying in my bill parking program . if i have 2 dates like this

t1 = datestr(datenum(now)); %answer is 13-Sep-2016 16:00:49
t2 = datestr(datenum(now)); %answer is 13-Sep-2016 20:00:14

i want to arithmetic (t2-t1) so i can get variable in hour or number . Please Help , Thanks b4 . I'm using matlab R2008a

Answer 1

[Walter Roberson]

Do not try to do date arithmetic on datestr . Do date arithmetic on the datenum values. The result will be in days. You can use datevec() or datestr() or plain arithmetic to convert the day difference to whatever form you prefer.

(Side note: now() returns a datenum directly.)

[obstac]

Thanks for quick reply , i've tried your suggestion to use datenum . and still confuse to convert it to hours , if i convert it use function hour , the answer is not i want to . do you have any suggestion please ?

[Walter Roberson]

t1 = datenum('13-Sep-2016 16:00:49');
t2 = datenum('13-Sep-2016 20:00:14');
time_diff = t2 - t1;
hours = floor(time_diff * 24);
minutes = round(time_diff - hours / 24);
fprintf('%d hours, %d minutes\n', hours, minutes);

[obstac]

thank you sir , it works very well :)

Answer 2

[Peter Perkins]

This doesn't help the OP (sorry obstac) who's using R2008a, but the same calculation using datetime:

>> t1 = datetime('13-Sep-2016 16:00:49')
t1 = 
  datetime
   13-Sep-2016 16:00:49
>> t2 = datetime('13-Sep-2016 20:00:14')
t2 = 
  datetime
   13-Sep-2016 20:00:14
>> time_diff = t2 - t1
time_diff = 
  duration
   03:59:25
>> [h,m,s] = hms(time_diff)
h =
     3
m =
    59
s =
    25