Time Stamp in LabVIEW is off by 300 years...

[c_w_k]

Hello,

One of my many questions is on creating a timestamp in LabVIEW....

I'm getting a value from a C++ DLL that returns the seconds since 01/01/1970 ("epoch"). I'm then trying to use the LabVIEW "SecondsToDate/Time" vi to convert this to a readable time format. When I do this the date is off by 300 years.....is there a trick to doing this? Is the labVIEW "SecondsToDate/Time" vi capable of converting time from 01/01/1970 or does it use a different date to convert from??

I'm wondering if it may be easier to create a timestamp just by using labVIEW instead of trying to convert the epoch variable that is returned by the C++ dll? For example my vi is gathering data constantly from a device, instead of taking the epoch variable from the C++ code I think I could possibly create a labVIEW time stamp each time the vi collects data........my first choice would be to convert the epoch variable that is provided from the C++ DLL.....

so any help on taking a C++ variable and converting it into a timestamp in LabVIEW would be greatly appreciated...

I've attached below, the code that I have so far....

-CK

[ned]

I'm getting a value from a C++ DLL that returns the seconds since 01/01/1970 ("epoch"). I'm then trying to use the LabVIEW "SecondsToDate/Time" vi to convert this to a readable time format. When I do this the date is off by 300 years.....is there a trick to doing this? Is the labVIEW "SecondsToDate/Time" vi capable of converting time from 01/01/1970 or does it use a different date to convert from??

If you read the help for the LabVIEW Seconds to Date/Time, you'll see that LabVIEW's "epoch" date is 12:00 a.m., Friday, January 1, 1904. You can determine the number of seconds between your epoch date and LabVIEW's, then add that amount before doing the conversion. Also make sure to use a numeric format with enough bits to store your number of seconds, taking LabVIEW's epoch date into account.

[c_w_k]

1970 epoch = 21600 (hopefully these are right, found them on a website that calculates epoch dates)

1904 epoch = -2082823200

======================

difference of -2082844800

so I added -2082844800 to the variable that is sent in from my C++ DLL......and I now get a year of 2246, which isn't as bad as being off by 300 years....but i've still got a ways to go.....the DLL is getting the value from a device simulator so I wonder if it is sending a bogus number.....

[Cat]

so I added -2082844800 to the variable that is sent in from my C++ DLL......and I now get a year of 2246, which isn't as bad as being off by 300 years....but i've still got a ways to go.....the DLL is getting the value from a device simulator so I wonder if it is sending a bogus number.....

2082844800 is within an hour (+/- for DST). I use 2082848400 for talking with Linux/Solaris systems and that works correctly. Do you know for sure that your dll is returning the correct value?

[Phillip Brooks]

If the remote device is sending you a value that is the number of seconds since 1/1/1970 00:00:00, then create a timestamp constant on the block diagram, and set the value to 1/1/1970 00:00:00. Use the add primitive to combine the epoch with the DLL seconds.

LabVIEW tip: easy relative timestamp calculations

Edited December 22, 2009 by Phillip Brooks

[Rolf Kalbermatter]

1970 epoch = 21600 (hopefully these are right, found them on a website that calculates epoch dates)

1904 epoch = -2082823200

======================

difference of -2082844800

so I added -2082844800 to the variable that is sent in from my C++ DLL......and I now get a year of 2246, which isn't as bad as being off by 300 years....but i've still got a ways to go.....the DLL is getting the value from a device simulator so I wonder if it is sending a bogus number.....

How big is your number then? As you can see 66 years (1970 - 1904) corresponds roughly to 2*10^9 seconds. From your 300 year difference I would guess you are not getting the number of seconds but rather something else such as the number of ms, since that ominous 1970 date.