Hi Jason:
If you are trying to modify date and time of your raw GNSS data, perhaps a different approach is to create a Rinex file of your data. You can then use a text editor such as Notepad or Wordpad to open and modify the Rinex "O" file. Once modified, the Rinex file can be re-imported to TBC. Although this can be time consuming (you will need to identify the required information in both the header and content of the O file, then edit things epoch-by-epoch), it is certainly do-able.
Regards,
Greg Hazelquist