At Scrooge's school the globe appears to label the island or Ireland as 'Eire' which term was not used until the 20th Century. This 'Christmas Past' scene would most surely have been set in the 18th century to have been Scrooge's childhood.
Marley's Ghost says the third spirit will come "when the last stroke of twelve has ceased to vibrate." However, he actually appears on the FIRST stroke of twelve.