Let me guess: offers can be sent by PM yesterday?
Stephen Hawking tried that in 2009 (when Bitcoin was created - coincidence?). See
mashable.com:
"I have experimental evidence that time travel is not possible," Hawking told reporters at the Seattle Science Festival in 2012. "I gave a party for time-travelers, but I didn't send out the invitations until after the party. I sat there a long time, but no one came."
What if those time travelers were smart enough not to go to the party because they might cause a rift in time and space because there was a change in the past. But considering the recent time travel paradox, if the time travelers were to go to the party then they will cause a change in the future which is going to change the timeline where the time machine was invented earlier or later which means that they didn't really went to the party resetting everything.