compare date and time

I need to check of the date is after specific date and time. for example

if (datestr(datenum(datetime))) > (datestr([2017 05 21 12 00 00]

datetime is array of date in the format 22-May-2017 12:00:00

Answer 1

[Star Strider]

I would just use the result of datenum.

Comparing strings will probably not work as you would want it to.

Answer 2

[Kathy]

without the datestr it gives this output for datestr(datenum(datetime)) and (datestr([2017 05 21 12 00 00])

out 7.3683e+05

   7.3684e+05

[Star Strider]

The two dates are a day apart, so that seems correct. You can do numerical operations and logical comparisons on the date numbers, including comparisons other than isequal, the only one you can do with strings (using the strcmp function).

Example —

date_dif = datenum('22-May-2017 12:00:00') - datenum([2017 05 21 12 00 00])

date_dif =
     1

If you want to see the complete date number, type :

format long g

in your Command Window.

Answer 3

[Steven Lord]

Don't convert from a datetime into a serial datenum and then to a datestr to compare them. Just compare the datetime variables directly. For instance, with a little nod to Abbott and Costello:

>> pitching = datetime('tomorrow');
>> catching = datetime('today');
>> pitching > catching
ans =
  logical
   1

Answer 4

[Peter Perkins]

All you need is

if theDate > '21-May-2017 12:00:00'

That's it. Unless you are using a fairly old version of MATLAB, stay away from datenum and datestr.