They weren’t waiting for him on the first day. That was enough for him to know there would be a problem. During the next year he would send a message back. The world he had left would depart from the one he had arrived in. No-one knew what would happen to him and his divergent universe after had sent the message.
He spent a week researching the events of the last year, checking whether the divergence point had already passed. Too much seemed the same. As he suspected, the moment was yet to arrive. As soon as he knew this, he raided a safety deposit box set aside for just such an eventuality and indulged in a week long debauch.
It was impossible to send anyone or anything back in time. The energy requirements were too much and the anomalies created would collapse the launching universe. However, it was simple to send someone forward, so that’s what they did.
One year was deemed the optimum distance, far enough to give ample warning but not so far that future shock was a risk. If the volunteer sent nothing back in their year in another country they would be met on the day they arrived. As yet, the paradox had never been tested or questioned.
He rented an apartment, bought a computer and got an internet connection and subscriptions to all the main news sources. He resisted the desire to sink into substance abuse, but he had more than enough money to pay for the finest food and, occasionally, the best prostitutes.
Then he just settled in and waited, for whatever calamity was to come.