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Usually April 23...
... but if it's April 23 at 06:00 in Sydney, it's April 22 in England, and if it's April 23 at 9 PM in New York, it's April 24 in England.
April 23 1950 was a Sunday.
April 23, 1963 was a Tuesday.
April 23, 1940, was a Tuesday.
April 23, 1974 was a Tuesday.