Charley's realization of Time Travel

Observing the surroundings
Charley ascertained the fact that he had actually been transported back in time by observing his surroundings. He noticed that the architecture, clothing, and transportation of the people around him were all from an earlier time period. For instance, the cars were old-fashioned and the women wore long dresses.

Interaction with people
Charley's interaction with people also helped him realize that he had traveled back in time. He spoke to a woman who had never heard of the Third Level, a modern transportation system. He also spoke to a news vendor who was selling newspapers from years ago.

Comparison with the present
Charley realized that he had traveled back in time by comparing the current time with the time he was in. He saw that the people were not familiar with the current trends, technologies, or events. He also noted that the prices of commodities were much lower than they were in the present.

Feeling of confusion and disbelief
Initially, Charley was confused and disbelieved that he had traveled back in time. He thought that he was hallucinating or had gone insane. However, as he continued to observe and interact with people, he realized that he had indeed traveled back in time.

In conclusion, Charley's observation of the surroundings, interaction with people, comparison with the present, and feeling of confusion and disbelief helped him ascertain the fact that he had actually been transported back in time.