How to convert Universal time to Local time?

Dear All,

I am trying to convert Universal time to local time. I used this function

% Convert time values to datetime array
    timeDatetime = datetime(selectedData(:,3)./3600, 'ConvertFrom', 'epochtime', 'Epoch', '1970-01-01');
    
    % Apply time zone offset to datetime array
    timeLocal = tzoffset(timeDatetime, 'EST','5');

but I got an error " Too Many input arguments".

Does anyone knows how to resoolve it?

Thank you,

Ara

[Jeffrey Clark]

@Ara, tzoffset only takes one input. You should be able to "convert" timeDatetime to EST by just setting its TimeZone attribute to 'America/New_York' (if you want EST/EDT otherwise Etc/GMT+5 ) before referencing the data from it, as in the following. Note that the timeDatetime creation will assume your local TimeZone and therefore the setting of TimeZone to somthing that is the same will result in the same values being reported (e.g., selectedData(:,3)./3600 will be assumed to be in your local time so you would probably want to set it in the datetime call as indicated.)

% Convert time values to datetime array
    timeDatetime = datetime(selectedData(:,3)./3600 ...
                           ,'ConvertFrom', 'epochtime', 'Epoch', '1970-01-01' ...
                           ,'TimeZone','Etc/UTC')
    
    % Apply time zone offset to datetime array
    timeDatetime.TimeZone = 'America/New_York'

[Ara]

Hi Jeffrey Clark,

Thank you for your useful explanation and the code.

What if I want the local time for AFrican, Asian, Pacific regions?

My time is in Universal time not local time but I want the plot in local time.

The figure is like this. I want it from 0-24 LT

[Steven Lord]

dt = datetime('now', 'TimeZone', 'local')

dt = datetime
   27-Dec-2022 14:55:52

dt.TimeZone

ans = '+00:00'

dt.TimeZone = 'America/New_York'

dt = datetime
   27-Dec-2022 09:55:52

dt.TimeZone = 'local'

dt = datetime
   27-Dec-2022 14:55:52

[Ara]

Hi Steven,

Thank you for the code but I got thi error:

Invalid expression. Check for missing multiplication operator, missing or unbalanced delimiters, or other syntax error. To construct matrices, use brackets instead of parentheses.

Would you please tell me how to resolve it?

Answer 1

[Jan]

The command tzoffset accepts one input only:

[dt,dst] = tzoffset(t)

Therefore the additional arguments 'EST','5' are not valid.

Maybe you mean

T = datetime(selectedData(:,3)./3600, ...
      'ConvertFrom', 'epochtime', 'Epoch', '1970-01-01', 'TimeZone', 'UTC');
T.TimeZone = 'America/New_York';  % Set accordingly, perhaps 'system'

[Ara]

Hi Jan,

Thank you for your response.

I used the code that you mentioned above. The result is like this, I want time from 0-24 but the time that gave me is for 20 min. Please see the figure attached.

[Eric Sofen]

That looks like a problem with your conversion from epoch time, but without knowing the values of selectedData, it's hard to know what the appropriate conversion factor should be.

[Ara]

Hi Eric,

Thank you for your comment.

Here is the selected data:

select = ~isMasked & selectElevation & selectPRN ;

selectedData = gpsData{stationId}.data(select,:) ;