Messages from Usenet group comp.lang.idl-pvwave, compiled by Paulo Penteado
Dear IDLers, I'm looking for an explanation of an odd file time thing. A few days ago I saved a file on my Windows computer at 23:56 (mins:secs). The modified-time shown in the file properties matches exactly. The structure returned by the FILE_INFO function shows 2 hours less in the MTIME tag, since it is based on UTC. My computer is set to "W. Europe Daylight Time". The command "print,SYSTIME(0,INFO.MTIME)" (where INFO is the result from FILE_INFO) shows exactly the right time. So far so good. However, there is another file, I saved on a day in last december at 23:30. The file properties show 00:30 of the next day. Looks like Windows is a little bit stupid, saved the UTC-time in December and now calculates the local time according to the daylight saving time. But the explanation does not seem to be so easy. The MTIME tag from the FILE_INFO structure results in 23:30. It would expect 22:30, because it's UTC. The SYSTIME function (without UTC-keyword) shows 01:30 of the next day. The SYSTIME function considers 2 hours difference because now is daylight saving time. This would explain an error of 1 hour, but not 2 hours. The question is, why is the MTIME value 1 hour to great? For a better overview, here are the time values in a table: File from October File from December ----------------------------------------------------------- My clock 2014-10-05 23:56:41 2013-12-19 23:30:03 File properties 2014-10-05 23:56:41 2013-12-20 00:30:04 MTIME (UTC) 2014-10-05 21:56:41 2013-12-19 23:30:04 SYSTIME(...) 2014-10-05 23:56:41 2013-12-20 01:30:04 Cheers, Heinz