Conversation so far:
What was Wallis Simpson's relationship with Edward VIII?
In January 1934, while Lady Furness was away in New York City, Wallis Simpson allegedly became Prince Edward's mistress.
Were Wallis Simpson and Edward VIII romantically involved?
Edward denied this to his father, despite his staff seeing them in bed together as well as evidence of a physical sexual act.

Question: When did they marry?
Self-contained rewrite: When did Wallis Simpson and Edward VIII marry?