How do I convert seconds since specific yyyy-mm-dd HH:MM:SS into date string?

I am extracting some parameters from a NetCDF file for use with some other software.

The time data is given as seconds since 2012-03-01 00:00:00 +00:00 in increments of 1200 seconds.

How do I create a variable containing date time data as yyyy-mm-dd HH:MM:SS? (the format required by the other software I am using)

I have tried:

DateTime=datestr(t+datenum(2012,03,01,0,0,0))

The output i get is wildly wrong, advancing in increments of approx. 3-4 years rather than increments of 20 minutes.

I plan to use this time data as a column in a CSV file.

I am completely new to Matlab prior to starting this project so if what i am doing doesnt make sense i apologise and appreciate any and all pointers!

Answer 1

[the cyclist]

t = [0 1200];
convertedDateTime = datetime(2012,03,01,0,0,t)

convertedDateTime = 1×2 datetime array
   01-Mar-2012 00:00:00   01-Mar-2012 00:20:00

The output will be in the datetime array format, which is the canonical method to store times in MATLAB. (There are many older ones as well, but this is best.)

[Ant376]

I changed

t = [0 1200]

to

t = [OriginalTimeVariable]

and it converted all entries. Thank you!

[the cyclist]

Happy to help. Just as an FYI, your original method would have worked, but the datenum is a count of days, so to correctly add an array measured in seconds to it, you needed

t = [0 1200];
dt=datestr(t/86400+datenum(2012,03,01,0,0,0))

dt = 2×20 char array
    '01-Mar-2012 00:00:00'
    '01-Mar-2012 00:20:00'

because there are 86,400 seconds in a day. However, the resulting character array (or even just the datenum format) is not as well suited to future calculations. It is much better, to use the canonical format, and learn the associated functions for handling datetime values.

[Steven Lord]

Another way to do this that may be more intuitive to read is to use datetime and duration arithmetic:

baseTime = datetime(2012, 3, 1);
convertedTime = baseTime + seconds([0 1200])

convertedTime = 1×2 datetime array
   01-Mar-2012 00:00:00   01-Mar-2012 00:20:00

That second line clearly is adding some number of seconds to baseTime.