Conversion of dates to a different format

Hi,

I need to convert 20110530 (2011 May 30) to 2011150 (which is the 150th day since January 01, 2011). How can i perform this task in MATLAB?

Answer 1

[Star Strider]

The new date and time functions probably have built-in functions to do what you want, but in their absence, this works:

t_str = '20110530';
dn = datenum('20110530', 'yyyymmdd');
dnstart = datenum(dt_str(1:4), 'yyyy');             % Start Of 2011
dayofyear = dn-dnstart+1
Result = sprintf('%4s%03d', dt_str(1:4),dayofyear)

Result =
2011150

The +1 is necessary for ‘dayofyear’ because it computes the difference between 01-Jan-2011 and doesn’t include 01-Jan-2011.

EDIT — Added ‘Result’ assignment.

[Damith]

OK. Thanks. How can I write the output as '2011150'? In this case 2011<dayofyear>?

[Star Strider]

My pleasure.

To write it as a string, use the ‘Result’ in my code. (The quotes do not display.) The initial string construction is the easiest way to create it.

To convert it to a number, this works:

ResultNr = str2num(Result)

To convert it to a cell (that will display the quotes), just put curly braces {} around ‘Result’.

[Damith]

Thanks again.

[Star Strider]

As always, my pleasure.

Answer 2

[Peter Perkins]

In R2014b or later, use datetime.

Convert a yyyyMMdd string to a datetime:

>> d = datetime('20110530','Format','yyyyMMdd')
d = 
   20110530

Change its display format to show day of year:

>> d.Format = 'yyyyDDD' % includes a leading zero for dates before 10 Apr
d = 
   2011150

Get the day of year as a number:

>> day(d,'dayofyear')
ans =
   150

Convert to string (though you likely don't need to do this unless you're exporting to outside of MATLAB):

>> char(d) % or use cellstr for multiple dates
ans =
2011150

Convert a number in yyyyMMdd format to a datetime:

>> d = datetime(20110530,'ConvertFrom','yyyyMMdd')
d = 
   30-May-2011 00:00:00

[Damith]

Thanks.