Change datetime display format

I have a julian date that I convert to a MATLAB datetime variable using:

tj = 2.456870501842000e+06;
mtime = datetime(tj,'ConvertFrom','juliandate','TimeZone','UTCLeapSeconds')

This creates the datetime variable "mtime" displayed as 2014-08-01T00:02:39.149Z. I want to change the display format of mtime (for plotting purposes) to show only hour:minute,

mtime.Format = 'HH:mm';

But I get this error:

The date format for UTCLeapSeconds datetimes must be 'uuuu-MM-dd'T'HH:mm:ss.SSS'Z''.

So is it not possible to change the display format of a datetime variable?

Answer 1

[Star Strider]

It is possible. It just takes some coding gymnastics:

tj = 2.456870501842000e+06;
mtime = datetime(tj,'ConvertFrom','juliandate','TimeZone','UTCLeapSeconds', 'Format','uuuu-MM-dd''T''HH:mm:ss.SSS''Z''')
ltime = mtime;
ltime.TimeZone = 'local';
ltime.Format = 'HH:mm'

producing:

ltime = 

  datetime

   18:02

Set ‘TimeZone’ to be whatever you want it to be.

[Orion]

Thanks for the answer. To clarify, I want to keep the time zone as 'UTCLeapSeconds', and only show the 'HH:mm' (00:02) part of the time as a tickmark label. I don't want to show the full time (eg: 2014-08-01T00:02:39.149Z) on the plot because in that format, a single one covers the entire axis while there are several tickmarks.

[Star Strider]

Simple enough. Just change the time zone back to UTC instead of local:

tj = 2.456870501842000e+06;
mtime = datetime(tj,'ConvertFrom','juliandate','TimeZone','UTCLeapSeconds', 'Format','uuuu-MM-dd''T''HH:mm:ss.SSS''Z''')
ltime = mtime;
ltime.TimeZone = 'UTC';
ltime.Format = 'HH:mm'

producing:

ltime = 

  datetime

   00:02

.

[James Tursa]

Note that this proposal doesn't preserve the leap second information, so it is not a solution.

mtime = datetime(1972,6,30,23,59,60.5,'TimeZone','UTCLeapSeconds')

mtime = datetime
   1972-06-30T23:59:60.500Z

ltime = mtime;
ltime.TimeZone = 'local';
ltime.Format = 'HH:mm'

ltime = datetime
   23:59

ltime.TimeZone = 'UTCLeapSeconds'

ltime = datetime
   1972-06-30T23:59:59.500Z

Everything has to stay in the UTCLeapSeconds time zone with the required Format to preserve the leap second. There is no direct solution to OP request using datetime as far as I know that keeps the leap second intact.