Things You'll Need
Instructions
Download a PS3 timestamp generator. It is a tool that can be found on many PlayStation forums as well as some user generated sites.
Enter the corrected date and time in the six text boxes. The order should be year, date, month, hour, minute and seconds. The year must contain four digits and all of the other boxes must be filled with two digits.
Hit the ̶0;Generate̶1; button, which will cause a code to become available in the box under the ̶0;Generate̶1; key.
Choose ̶0;Copy̶1; under the new code. This gives you the hex code you need.
Open your TROPUSR.DAT on the PS3 with the hex editor. If you do not have one, it can be downloaded online for free.
Paste your generated code or ̶0;hex̶1; underneath where the hex editor lists the trophy ID.
Save the new data.
Open your FTP manager from the home screen and overwrite your current TROPUSR.DAT file with the newly saved file. This does not happen automatically like when you save straight from the computer.