Convert epoch to human readable data and time

Hi,

i have a vector of time in epoch format (read as double in Matlab). I have to convert all the elements in a format HH:MM:SS till milli or even nano seconds if it is possible.

The vector time is related to data acquired on 20th October 2021.

Can someone help me please ?

Thank you in advance

[Star Strider]

What is the epoch time for midnight on 20th October 2021, and 1 and 60 seconds later?

.

Answer 1

[Spectro]

Have a look at datetime() using parameter "ConvertFrom":

epochs = [1638351674 1638351674];

datetime(epochs, 'ConvertFrom', 'epochtime')

[Giorgia Fusaroli]

Thank you !

I already tried this solution, but then i had this error:

Conversion to or from epoch times is not supported for times that more
than 285Ky before or after the specified epoch

Do you have any idea about how can i solve this ?

[Spectro]

Well, try 'posixtime' instead of 'epochtime'. Do you get the same error then?

[Giorgia Fusaroli]

no, but then the output is in the follow format:

5.1802e+10 CE

And i don't even know what it means :(

[Spectro]

Attach the data please.

Answer 2

[Giorgia Fusaroli]

FYI

I solve the problem in this way:

epochs = uint64(vector-of-epoch-data)
datetime(epochs,'ConvertFrom','epochtime','TicksPerSecond',1e9,'Format','dd-MMM-yyyy HH:mm:ss.SSSSSSSSS');

Answer 3

[Steven Lord]

What's the unit of time a value of 1 in your epochtime represents? Seconds, microseconds, nanoseconds, etc.?

t = 6000;
start = datetime('today') % Use midnight today as the start of the epoch

start = datetime
   01-Dec-2021

dt1 = datetime(t, 'ConvertFrom', 'epochtime', 'Epoch', start) % 6000 seconds after the epoch

dt1 = datetime
   01-Dec-2021 01:40:00

dt2 = datetime(t, 'ConvertFrom', 'epochtime', 'Epoch', start, ...
    'TicksPerSecond', 1000) % 6000/1000 seconds after the epoch

dt2 = datetime
   01-Dec-2021 00:00:06

You may also want to look at the table in the entry for the dateType input argument to datetime to see if one of the provided options matches what your time data represents: 'ntp', '.net', or 'ntfs' perhaps, since they each represent a number of "clock ticks" that are a small fraction of a second?