How to remove decimals digits from datetime arrays?

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Hi,
I have a datetime array in the format 'yyyy-MM-dd HH:mm:ss.SSS', and I want to round down or remove only the third decimal digit. E.g. the output should be 'yyyy-MM-dd HH:mm:ss.SS'. It seems that I cant use functions like round, floor or ceil in datetime arrays, as it prompts an error message that suggest I use dateshift instead. However, dateshift does not seem to handle rounding miliseconds (it works if I just wanted to remove/round all decimals, but that is not what I want... like I said, I am interested in keeping 2 decimal digits only).
I've tried converting the array into datenum or extract only the 'seconds' part as a double. Also tried to change just the format but that does not really remove the third digit from the database (it seems like it is only a visual change). I think there should be an easier way to do this. Does someone know how to do this?
  2 Comments
Guillermo Pérez Castro
Guillermo Pérez Castro on 26 Jan 2022
Hi, thanks for the reply, I am actually interested in changing the stored value, that is, to round the stored date/time information to 2 decimal digits instead of 3.

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Accepted Answer

Stephen23
Stephen23 on 26 Jan 2022
Edited: Stephen23 on 26 Jan 2022
Assuming that the goal is to truncate at some precision (which is totally independent of the FORMAT), then this works:
T = datetime(2022,01,02,03,04,05.6789, 'Format','yyyy-MM-dd HH:mm:ss.SSS')
T = datetime
2022-01-02 03:04:05.678
S = fix(mod(second(T),1)*100)/100
S = 0.6700
U = dateshift(T,'start','second') + seconds(S)
U = datetime
2022-01-02 03:04:05.670
Of course if you do not want to change the underlying data then you can simply change the FORMAT property.
  3 Comments
Guillermo Pérez Castro
Guillermo Pérez Castro on 26 Jan 2022
Thanks for the comment, but in this case, I do wish to truncate the decimals, so this solution will do just fine.

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