How to convert date to day number?

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miguel angel torres quintero 2017-7-28

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https://ww2.mathworks.cn/matlabcentral/answers/350606-how-to-convert-date-to-day-number

评论： Jan 2017-8-1

Hello I wanna convert a date to day number. For example: 2012-Junuary-12 is equal to 12 days (we are talking about 12 days passed of 365 day) I don´t refer to Julian Day.

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James Tursa 2017-7-28

编辑：per isakson 2017-7-28

@Jan: Julian Date and Day Of Year are two different things. Julian Date has a very specific meaning. E.g. from the USNO:

http://aa.usno.navy.mil/data/docs/JulianDate.php

Or if you prefer Wiki

https://en.wikipedia.org/wiki/Julian_day

Jan 2017-8-1

Thanks, James. I hoped that the OP explain maore details also, e.g. how the input is represented and why he mentions the Julian Day.

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回答（1 个）

Steven Lord 2017-7-28

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/350606-how-to-convert-date-to-day-number#answer_275932

在 MATLAB Online 中打开

dt = datetime('2012-January-12')
day(dt, 'dayofyear')

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Andrei Bobrov 2017-7-28

Peter Perkins 2017-8-1

在 MATLAB Online 中打开

And also:

>> dt = datetime(2012,1:3,12)
dt = 
  1×3 datetime array
   12-Jan-2012   12-Feb-2012   12-Mar-2012
>> dt.Format = 'yyyy:D'
dt = 
  1×3 datetime array
   2012:12   2012:43   2012:72