Note: This was done with v4.20. Note: This procedure requires editing a game file; creating a backup copy of the file before proceeding. Using a text editor, edit the "Plant<number>.hgp" file in the game directory. This file stores the seed information once they are planted, with the number being in the order you planted it. The date the seed is planted is stored in three bytes. Byte 41 stores the day number, 42 is the month and 43 stores the year in three digits. For example, 2008 is stored as "108", 2012 is "112", etc. Use a hex or text editor to alter the byte values to make your plants any age desired. Do this by subtracting from the date. You have to keep your plants watered or use Vacation mode as they will still die if you advance their age too far without watering them. This way you can alter the age of each plant individually and there is no need to change your computer's date.