datetime array concat not diplaying time of day when first element is NaT

Consider the following code ( Elements is a Matrix of DataValueElements, a self-defined class with the field DateTimes, an array of Matlab datetimes):

Example 1: (showing content of Elements)

>> {Elements(1:end,4).DateTimes}  
ans =   1×4 cell array
[NaT]    [01-Mar-2018 10:00:00]    [01-Mar-2018 10:00:01]    [NaT]

Example 2: (showing problem - time of day not displayed)

>> arr = [Elements(1:4,4).DateTimes]
arr =   1×4 datetime array
 NaT     01-Mar-2018   01-Mar-2018   NaT        

>> datetime(arr)
ans =   1×4 datetime array
NaT     01-Mar-2018 10:00:00   01-Mar-2018 10:00:01   NaT

Example 3: (problem doesn't occur when first element isn't NaT)

>> [Elements(2:end,4).DateTimes]  
ans =   1×3 datetime array
01-Mar-2018 10:00:00   01-Mar-2018 10:00:01   NaT

Why is the time of day not displayed when concatting the array and when the first element is NaT? Or is this a bug?

[Jan]

It would be useful if you provide some code to create the input data. Then the readers can check their ideas before posting.

Answer 1

[Jan]

This does not reproduce the problem:

c = datetime({'NaT', '01-Mar-2018 10:00:00', '01-Mar-2018 10:00:01', 'NaT'})

But why is it a problem at all? What about defining the Format property of the datetime object explicitly? The automatic detection of the format seems to fail, when the first value is a NaT, but if you want a specific output to the command window, using the magic disp of the ans object is weak at all.

Answer 2

[Peter Perkins]

What's going on is that you are concatenating four scalar datetimes, and the display format of the result is coming from the first, and that happens to ba a NaT, and that has been created with a display format that does not include time of day. Not sure where the NaT is coming from, but you can specify a format if you're creating it. If not, you can just adjust the format of your result after concatenating.

This is kind of an unusual case that has hit a rough edge of the format rules for datetime.