How to convert datestring with milliseconds in datetime matlab

Question

Hi I have a small problem with the datestring. My data is in a matlab table with about 2 million rows. The time comes in the format DateStrings='2014-06-23T17:06:41.584+0200'. I would like to have it in datenum . So I thought I can convert it to datetime using the following code and then convert it to datenum.

    t = datetime(DateStrings,'InputFormat','uuuu-MM-dd''T''HH:mm:SSSSSXXX','TimeZone','UTC');

however this does not work. With the same error message"Unable to parse date/time string using the format 'uuuu-MM-dd'T'HH:mm:SSSSSXXX'. I tried for a few strings to remove the miliseconds and then to code works. I dont really need the milliseconds so I was thinking to split the string and remove the milliseconds. However there comes the problem with the amount of data and I run into memory problems. Does anybody know how to do this in a smart way. kind regards Matthias

Can you convert the table to an array? Then you could just remove the last xxx chars, convert it back and then run datetime — rst

excaza excaza · Accepted Answer · 2015-09-23T13:37:15

Some of your formatting for datetime is incorrect.

Tweaked slightly:

DateStrings='2014-06-23T17:06:41.584+0200';  
t = datetime(DateStrings,'InputFormat','uuuu-MM-dd''T''HH:mm:ss.SSSXXXX','TimeZone','UTC');

Which returns:

t = 

   23-Jun-2014 15:06:41

EDIT:

Forgot about the second part of the question. To use datenum you'll again have to change the syntax slightly. I will also note that you can do this conversion on your strings without having to convert to a datetime array.

For example:

DateStrings='2014-06-23T17:06:41.584+0200';
t = datenum(DateStrings, 'yyyy-mm-ddTHH:MM:SS.FFF');
test = datestr(t, 'yyyy-mm-dd HH:MM:SS.FFF');

Which returns:

t =

   7.3577e+05

and

test =

2014-06-23 17:06:41.584

A final note on datenum is that there is no support for timezones. Since datenum represents the number of days from a fixed date we can add/remove hours simply:

DateStrings='2014-06-23T17:06:41.584+0200';
t = datenum(DateStrings, 'yyyy-mm-ddTHH:MM:SS.FFF');

hourstoshift = -2;
t = datenum(t + hourstoshift/24);
test = datestr(t, 'yyyy-mm-dd HH:MM:SS.FFF')

Which returns:

test =

2014-06-23 15:06:41.584

Here I've specified the hours to shift manually, but you could also parse your time and determine this automatically.

How to convert datestring with milliseconds in datetime matlab

1 Answers