String to Date Subtraction

Hello,

How do I subtract two dates that are in a string formatted like: 'Mon Feb 27 17:03:15 EST 2017' and 'Mon Feb 27 17:40:11 EST 2017' in matlab 2010a?

Answer 1

[Walter Roberson]

t1 = 'Mon Feb 27 17:03:15 EST 2017';
t2 = 'Mon Feb 27 17:40:11 EST 2017'

times = datetime({t1; t2}, 'InputFormat', 'eeee MMM dd HH:mm:SS z yyyy', 'TimeZone', 'America/New_York');

time_diff = times(2) - times(1)

The result will be a duration object containing 36 minutes 59 seconds

[Walter Roberson]

In R2010a you would need to parse the dates using datenum instead of datetime. That is going to be more difficult as datenum does not support time zones at all. Are all of the times EST, or are some of them EDT, or are there other time zones as well? Or can we count on the two times being in the same timezone?

Can we count on there always being two digits for the day of the month? Can we count on there being a leading 0 in the hour?

[Peter Perkins]

Walter, one slight change: the format should be

'eeee MMM dd HH:mm:ss z yyyy'

with a small s for seconds.

Answer 2

[Peter Perkins]

Walter's datetime suggestion returns a duration, which represents an exact, fixed-length amount of time. Depending on what you mean by "subtract", you might also look at between to get the difference in terms of calendar units:

>> times = datetime([2016 2017],[11 2],[19 27],[14 17],[53 40],[20 0])
times = 
1×2 datetime array
 19-Nov-2016 14:53:20   27-Feb-2017 17:40:00
>> between(times(1),times(2))
ans = 
  calendarDuration
   3mo 8d 2h 46m 40s
>> between(times(1),times(2),'weeks')
ans = 
  calendarDuration
   14w

[Walter Roberson]

Note, though, that these operations require R2013b or later.