all file dates changed when using this device

I have a brand new SanDisk Extreme Pro 3.1 256 GB drive using Windows 7.

I backed up and encrypted a whole folder from my desktop to USB drive, and then unencryted and installed thoses files from USB drive to my laptop.

Now every file in the folder has the date changed to the current date. This is not useful as I need to sort those hundreds of files by date.

Has anybody seen this or have a cure?