How to covert a datenum (serial number) back to original date time format

Question

Gali Musa 2018-6-14

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https://ww2.mathworks.cn/matlabcentral/answers/405702-how-to-covert-a-datenum-serial-number-back-to-original-date-time-format

回答： Peter Perkins 2018-7-5

I have a column of datenum and i want to change it back to the original date and time. i use DateNumber = datetime(time, 'ConvertFrom','datenum'); but the time is not the same with the original one. Sample example; time 01/01/2013 00:00 01/01/2013 00:15 01/01/2013 00:30 01/01/2013 00:45 01/01/2013 01:00 01/01/2013 01:15 01/01/2013 01:30 01/01/2013 01:45 01/01/2013 02:00 this is what i have in a multiple columns and i converted the string date to a serial in order to make the calculation. after i finished all the calculation want to return back the date and time to its original. Here is the sample for that

time 735235 735235 735235 735235 735235 735235 735235 735235 735235 735235 i used datenum sytax and here is it DateNumber = datenum(X)

i want to change the serialnumber back to its original position

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Jan 2018-6-14

Without knowing what "the original one" is, neither the readers in this forum nor Matlab can apply the wanted conversion. A datenum is a floating point values. It does not carry any magic information about how this number has been represented before.

Please edit the question and add the information, what you want to get exactly.

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Answer 1

Peter Perkins 2018-7-5

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https://ww2.mathworks.cn/matlabcentral/answers/405702-how-to-covert-a-datenum-serial-number-back-to-original-date-time-format#answer_327638

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There's not enough in your description to go on, but a round-trip certainly does work in your example:

>> dn = 735235 + (0:15:120)/1440
dn =
  Columns 1 through 4
                    735235          735235.010416667          735235.020833333              735235.03125
  Columns 5 through 8
          735235.041666667          735235.052083333               735235.0625          735235.072916667
  Column 9
          735235.083333333
>> d = datetime(dn,'ConvertFrom','datenum')
d = 
  1×9 datetime array
Columns 1 through 5
   01-Jan-2013 00:00:00   01-Jan-2013 00:15:00   01-Jan-2013 00:30:00   01-Jan-2013 00:45:00   01-Jan-2013 01:00:00
Columns 6 through 9
   01-Jan-2013 01:15:00   01-Jan-2013 01:30:00   01-Jan-2013 01:45:00   01-Jan-2013 02:00:00
>> dn2 = datenum(d)
dn2 =
  Columns 1 through 4
                    735235          735235.010416667          735235.020833333              735235.03125
  Columns 5 through 8
          735235.041666667          735235.052083333               735235.0625          735235.072916667
  Column 9
          735235.083333333
>> dn - dn2
ans =
     0     0     0     0     0     0     0     0     0