# Convert ordered date to formal matlab date

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Tunechi on 14 Oct 2014
Commented: Sean de Wolski on 15 Oct 2014
How to convert the following sequence of date to formal y/m/d or Matlab date format

José-Luis on 14 Oct 2014
Note that you'd still need the year. But if you know that then:
your_date = datenum(your_year-1, 12, 31, 0, 0, 0) + ordinal_day;
Ordinal_day goes from 1 to 365.
dpb on 14 Oct 2014
What about leap years? OP shows multiple years possible in his listing w/o a starting year hint. Of course, he may be ignoring them...
José-Luis on 15 Oct 2014
I assumed that if it was a leap year it'd say 366, but your point is valid.

Kelly Kearney on 14 Oct 2014
syear = 1900; % Year corresponding to first set of numbers
x = repmat(1:365, 1, 3)'; % Your data
yr = cumsum(x == 1) + (syear - 1);
dn = datenum(yr, ones(size(yr)), x); % datenumbers
If you want to format the date, you can use datestr:
>>datestr(dn(1))
ans =
01-Jan-1900

dpb on 14 Oct 2014
Edited: dpb on 15 Oct 2014
Don't try to "convert", just create. Given the first year and length of the list, the date number vector would simply be
ystrt=2000; % or whatever
dn=datenum(ystrt,1,[1:length(dates)].',1);
datenum is smart enough to roll over the days by month and year including leap years.

Sean de Wolski on 14 Oct 2014
Or in R2014b you can do this with the new and improved datetime class:
datetime(2014,1,1:365,0,0,0)'
dpb on 15 Oct 2014
OK, so you were merely intending to emphasize the class as a class rather than some really enhanced functionality.
Wonder how the class implementation compares to "deadahead" array function performance-wise. Altho datenum is notoriously slow for all it's checking perhaps TMW has cleaned up a bunch of that and it's as fast or even faster...my machine here is limited and R2012b brings it to just barely tolerable performance so I've not tried the later revisions and I'm not at all eager to change UI.
Sean de Wolski on 15 Oct 2014
The class does have some enhanced functionality, especially when it comes to plotting and time zones.
I haven't measured the performance of it. Maybe Peter will chime in.