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Re: problem parsing time out of datetime object

From: Nicholas Jankowski
Subject: Re: problem parsing time out of datetime object
Date: Fri, 20 Oct 2017 15:44:47 -0400

On Fri, Oct 20, 2017 at 3:41 PM, PhilipNienhuis <address@hidden> wrote:
AG wrote
> I am trying to parse a datetime string into two pieces, date and time, and
> I'm trying to figure out why this code does not work.  According to the
> docs
> it seems that a call to rem on a datetime will give you the time but it
> doesn't seem to do that.
> dt_num = datenum('2013/05/29 00:00:00','YYYY/DD/MM HH:MM:SS')
>  d_num = floor(dt_num)
>  t_num = rem(dt_num,1)
> datestr(d_num) ## ans = 05-Jan-2013  (RIGHT!)
> datestr(t_num)  ## ans = 31-Dec--001 (WRONG)

Seems perfectly OK to me. What else would you expect for a date in the year
0, month 0, day 0?  :-)

But perhaps you meant:
>> datestr (t_num, 13)
ans = 00:00:00

(try "help datestr" to see datestr's output options)


I would also suggest being careful with your upper and lower case format declarations. Octave is more forgiving than matlab, but usually the date should be lower case and the time upper case.  Also, did you mean to specify day = 5, month = 29? This can cause unintended results.

when there is no format specified for datestr, it tries to guess at the form to use. help says it chooses between 0, 1, or 16 depending on whether the date or time portion (portion before or after the decimal point) are empty. so: -->  dd-mmm-yyyy HH:MM:SS
xxx.0 -->  dd-mmm-yyyy -->  HH:MM:SS

This works correctly for non-zero time (try with any other time and the last command does just give the time). apparently, it interprets 0.0 as the second case, and displays the date '0', or 31 DEC 0001.  matlab interprets this as '00-Jan-0000'

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