Logical result false when comparing 2 identical times

Hello, i want to compare times and something is wrong and i dont know why. Perhaps something is wrong in the Excel format of the data. but in matlab i think i placed the format of all the time equal.

 clear;
clc;
close all;
tabela1 = readtable('galp.xlsx');
tabela2 = tabela1;
[n,m] = size(tabela1);
t_1 = datetime('01-01-2018 02:00','InputFormat','dd-MM-uuuu HH:mm');
t_2 = datetime('01-01-2018 06:00','InputFormat','dd-MM-uuuu HH:mm');
tempo_a_comparar = tabela2{121,1};
t_1
tempo_a_comparar
C = isequal(t_1,tempo_a_comparar)

[Jos (10584)]

If isequal returns false, they are, by definition, not equal.

I am not going to download your xls file, but you should be able to check for yourself using the debugging tools in matlab.

What do the two variables contain exactly?

[Jan]

@Tiago: Please explain, what you observe. Do you get e.g. error messages? Reading your question it does not get clear, why you assume, that there is something "wrong".

[Walter Roberson]

Subtract one from the other to see the time difference that MATLAB thinks exists.

[Tiago Dias]

@Jan Simon, thanks for your question, because now I saw that some are the month has a number "01" other is "Jan" and thats why it is false the return.

[bandari shravya]

Getting error on comparing both datetimes 
file2 = dir('matlabfiles');
filetest = struct2table(file2);
datemodified = datetime(filetest.date,'Format','dd/MMM/uuuu');
t1 =  '08-Feb-2019 13:10:15';
to = datetime('26-Feb-2019','Format','dd/MMM/uuuu');
 t2 = to ;
numfiles = length(file2);
for k = 1:numfiles
    fprintf('%s ..',datemodified(k));
    t2 = to ;
    d = datemodified(k);
    if isequal(d,t2)
        fprintf('Done.\n');
    else
        fprintf('NOT .\n');
    end
    
end

[Walter Roberson]

When you called datetime(filetest.date,'Format', 'dd/MMM/uuuu') then it converts the entire time and records it, and sets the format so that what is displayed for the time is in the format dd/MMM/uuuu . 'Format' of a datetime has to do with display, not with how it is used in computing or how the input is parsed. The parameter to control how a character vector is parsed is 'InputFormat', or sometimes 'ConvertFrom'.

You can use ymd() to extract the year, month, and day of a datetime, or you can use dateshift(d,'start','day') to refer to the beginning of the day.

Answer 1

[Peter Perkins]

The extension of the file you've posted does not match your code. The file you've posted appears to be a .xlsx file.

Add :ss.SSSSSSSSS to the end of all your formats. What you will see is this:

t_1 = 
  datetime
   01/01/2018 02:00:00.000000000
tempo_a_comparar = 
  datetime
   01/01/2018 02:00:00.000022949
ans =
  -2.2949e-05

My initial reaction was to point out that Excel stores time in units of days since 1900. So in general, timestamps read from Excel are accurate only to about

>> eps(seconds(datetime - datetime(1900,0,0)))
ans =
   4.7684e-07

seconds. But since the actual difference is 50 larger than that, I can only assume that what's in the .xlsx file is not what you think it is.

[Tiago Dias]

@Peter Perkins There is anyway to delete in matlab the SSSSSSS?

when I input the file from excel, I just want Matlab to read hours minutes and seconds, I don't want Matlab to read SSSSS, is that possible?

[Walter Roberson]

No, you need to read the SSSSS as well if you are dealing with text. However, you can

 DateTimeArray = dateshift(DateTimeArray, 'start', 'second')

[Tiago Dias]

yeah i found that as well in another question i asked, thanks a lot!