Unfortunately I need to adjust some of the dates which can be done easily using sqlite. Essentially log on the the trac database using the following command:
sqlite3 /path/to/trac/project/db
All dates and times in sqlite are stored as the number of seconds since 01-Jan-1970, therefore to subtract 5-days from the creation date you would run:
UPDATE ticket
SET time = time - (5*24*60*60)
WHERE id = n