I think it's a bug but i want to know before send report. Thanks
What kind of file is it?
Which date are you talking about?
mp3 file and modified date.
Oh i just notice that i have 10.0.1.4 installed 
I update...
It's the same thing with last beta...
Modified date changes everytime to 01/01/1601 02:08:56
For me, using 10.0.1.6, the modified timestamp on an MP3 file is set to the current date and time by SetAttr META *.
Try with some different MP3 files, and if you're using a network drive try on your local drive (in case the problem is a network storage device that doesn't set timestamps properly).
I try in local drive, in XP, with others files... same things... modified timestamp (01/01/1601 02:08:56) and creation too (01/01/1601 02:00:18). But in XP (fresh install), it's 30/12/1756 01:20:16 and 25/01/1660 15:49:25.
It could be a bug that's affecting different installs in different ways.
I noticed that, unlike other SetAttr META commands, this one seems to ignore Preferences / File Operations / Metadata / Update last modified file dates when setting metadata and instead always sets the time. I've flagged that with Jon, and maybe looking into that will reveal what you're seeing, even though I can't repro it myself.
Jon has fixed what I was seeing in an internal build, and looking at the code-change I think it explains what both of us were seeing.
(I suspect the different behaviour we saw on different machines was due to timezone settings.)
Try the next version once it's released and I think it will resolve the issue. If not, let us know and we'll look into it further.
Perfect (as always)
Now waiting...
It's solved with 10.0.2.0. Thanks