Time format in seconds since 0-Jan-0000

Dear Matlab community,

I find myself having to work with a time format expressed in seconds since 0 January 0000. Or at least, I believe so. The given value equals 6.375053639947000e+10, which is indeed the amount of seconds in roughly 2020 years. Unfortunately, I can't find any Matlab function that could convert this into a 'normal' date and time.

Hopefully someone could help me out here,

Kind regards

Jan

[James Tursa]

You need to be careful with this. What is your time frame? Do you have an example where you know an exact pair of time & calendar date so you can figure this out?

[Jan Vandendriessche]

I'm afraid I don't. The origin of the time variable is the start of some measurements carried out with a GeoSIG accelerometer. This was done on the 3rd of march this year, somewhere near 11am.

[James Tursa]

If you don't have an example pair of time & date, or some other definitive description of what the time frame is, then you will never be able to convert it with certainty. The best you can hope for is a conversion that gets you close to what you think is correct, but might not be correct.

What computer system & software was this accelerometer connected to when the measurements were made? Maybe that will give you a clue about the time frame used.

Answer 1

[Cris LaPierre]

You could use datetime.

d = datetime(0,0,0,0,0,6.375053639947000e10)

d = 
   01-Feb-2020 10:19:59

[Jan Vandendriessche]

Thanks a lot. I didn't know about this feature of the datetime function. Unfortunately the corresponding time should be somewhere near 11am on 03-Mar-2020, so I'm afraid there must be something else going on.

[Walter Roberson]

Solar time?

leap year issues?

Gregorian vs Julian would account for 13 days

[Cris LaPierre]

I did little more playing around. Looks like datetime(0,0,0,0,0,0) is not what I expected:

d0 = datetime(0,0,0,0,0,0)

d0 = 
   30-Nov--0001

Since the date was off ~31 days, it got me thinking if I could make the date at least start January 1, I might get closer. I came up with 2 options

% Set month to January. Is Dec 31 -0001, or 1 day before Jan 1, 0000.
d0 = datetime(0,1,0,0,0,0)

d0 = 
   31-Dec--0001

% Use that same format when converting seconds
d = datetime(0,1,0,0,0,6.375053639947000e10)

d = 
   03-Mar-2020 10:19:59

Another way to get the same result is to sepcify the epoch and clock ticks using datetime. Now that I have an idea what the epoch value should be.

d2 = datetime(6.375053639947000e10,'ConvertFrom',...
    'epochtime','Epoch','-0001-12-31','TicksPerSecond',1)

d2 = 
   03-Mar-2020 10:19:59

[Jan Vandendriessche]

Wow, thanks a lot! This should be almost spot on. Very much appreciated!