Conversation so far:
Who was Robert Lincoln?
Robert Todd Lincoln was an American politician, lawyer, and businessman and the first son of President Abraham Lincoln and Mary Todd Lincoln
How was Robert Lincoln rescued?
Edwin Booth saved Abraham Lincoln's son, Robert, from serious injury or even death. The incident occurred on a train platform in Jersey City, New Jersey.
How did Edwin Booth's rescue of Robert Lincoln all come to light?
Robert Lincoln recalled the incident in a 1909 letter to Richard Watson Gilder, editor of The Century Magazine.
Did Edwin Booth win any award or honor for this act?
The fact that he had saved the life of Abraham Lincoln's son was said to have been of some comfort to Edwin Booth following his brother's assassination of the president.
Where did Edwin Booth rescue Robert Lincoln?
The incident where Edwin Booth saved Robert Lincoln occurred on a train platform in Jersey City, New Jersey

Question: When did this happen?
Self-contained rewrite: When did Edwin Booth's rescue of Robert Lincoln happen?