When was Saint Barbara canonized as saint?
St. Barbara, if she really existed, would have been declared a saint shortly after her martyrdom. However, there is virtually no evidence that she really existed and her name was removed from the Calendar of Saints and her cult surpressed in 1969.
Barbara of Nicomedia was never formally canonized as the process was not in place before the 12th century. She would have been proclaimed a saint by local church authorities based on public acclaim. Barbara was removed from the Calendar of Saints and her cult suppressed in 1969 for lack of credible evidence that she had existed. Her recorded life is more mythical than factual.