What you do is pick a date that is special to you for some reason and celebrate on that day if you want to celebrate your coming to Satanism or breaking free from the enemy. You dont even have to use the date of your dedication for this. You also don't need to know the exact date I dont think.
I chose July 21st cause its around the time I got out of a bad situation with Drugs for good and started to change my life for the better 4 years ago and its when the final rtr was posted etc. Its also around when I came back to Satanism after straying for a bit So I feel it is a good day to celebrate my dedication and being free even though I do not know exactly when I dedicated it had to be Augest to September I would think from what I remember about the weather but totally not sure.
Do something like this if you want. Giving you an example of what i did.