Hi azpix, I assume you have all the photos on the wrong date/time. If so, go to the Library or Grid view mode (hit "E" or "G" on your keyboard). Select all the photos you know have the wrong date/time and go to the top to the tab "Metadata" and find "Edit Capture Time".
Here you can easily change the date/time. I usually take option 1 "Adjust to a specified date and time". It will adjust the picture date/time from the one displayed, all others will be changed accordingly (meaning if image 2 was captured 1 hour later, it will change that image to the specified date/time +1 hour). Hit change. You will get a message that this operation can't be undone, hit OK - I have rolled back the time successfully in the past, should you have missed the date somehow.
I generally use the option to synchronise mutliple cameras during event shooting.
Azpix, Did it work, or do you still have issues? if it is right, please mark as "right answer".