Environment: EagleFilter 1.6.1, Mac OS 10.9.1, Retina MBP Early 2013, 16GB RAM
When editing in the EF Info pane, the oldest date entry that I can set is 12/31/2000. Any time I set the date older, it resets to 12/31/2000. When I inspect the underlying files creation date in the Finder (EF -> Show in Finder -> Get Info), it shows the older creation date.
Thanks for the report, however I have not been able to reproduce this bug on my Mac. Does this happen if you create a new library with a new file and try to set its date? When (and where) exactly do you see the date change in EagleFiler? Do you see any errors in the log? The “12/31/2000” makes it sound to me like the file is not where EagleFiler was expecting to find it, or else there’s a file permissions problem; EagleFiler shows that date if there’s an error reading the file.
video showing the error
A video showing the error is here: http://youtu.be/9dl576wTjbA
There are no errors in the log file, save for the flurry of interesting ones generated while running, ironically enough, the QuickTime Player to capture the screen activity. 
I did check this against another EagleFiler library, and it too exhibited the same symptoms. In list view, anything with a date older than 12/31/2000 was shown as 12/31/2000.
The only “unusual” thing perhaps about my setup is storing all my EagleFiler archives in encrypted sparse bundles, but I’m hoping that’s not all that unusual (for backup, sync, and security).
Thanks for the report. I’m not sure why it was working correctly for me earlier, but now I am able to reproduce this problem. Please send me an e-mail so that I can let you know when a fix is available.
No, encrypted sparse bundles work very well, and I’ve also reproduced the problem with an unencrypted library.
This is fixed in EagleFiler 1.6.2.