SAS - Creation / Modified Datetime - Platform Differences

[curtisalexander]

When I call the function readstat_get_creation_time (or readstat_get_modified_time) on a sas7bdat file, I get different values returned depending upon whether I am executing on Windows or on Linux.

For example, using the file somedata.sas7bdat I get the following for the creation time on Windows vs. Linux.

Platform	Creation Time (Raw)	Creation Time (Formatted)
Windows	1538393035	2018-10-01 11:23:55
Linux	1222795436	2008-09-30 17:23:56

When opening the somedata.sas7bdat file in SAS itself, it notes that the creation time is 2008-09-30 17:23:56.

Finally, I am using the latest dev version — abb31aa.

My suspicion is I have a discrepancy in the C types. I'll continue researching myself but any thoughts about what could be the root cause?

As always, thanks for the project and your time!

[evanmiller]

I would look around here:

ReadStat/src/sas/readstat_sas.c

Lines 162 to 163 in 69f5518

	struct tm epoch_tm = { .tm_year = 60, .tm_mday = 1 };
	time_t epoch = mktime(&epoch_tm);

My guess is that Windows can't handle a negative time value (i.e. pre-1970) and returns -1 for the SAS epoch of 1 Jan 1960. We could probably update the logic to hard-code the number of seconds between 1 Jan 1960 and 1 Jan 1970 instead of computing it on the fly.

[evanmiller]

Try the fix in #240. Thanks!

[curtisalexander]

@evanmiller - Fix in #240 fixes the issue described here. Tested same dataset on my Windows and Linux machines and the dates now match (as well as match what SAS suggests).

Hopefully it can be added to the next RC for 1.1.6. Thanks so much!