Miranda cuts the Valentine's Day cake with a clean kitchen knife. However, the next shot shows the cake cut down the middle, and the same knife lying beside it clean and bare, as if it had never been used.
Although accurately following the book (and a good indication that this is indeed a fictional story), to make the days & dates actually match up you need to either move to 1903 or 1874, as those are the closest years that had Feb 14 on a Saturday (and March 27 on a Friday)
The movie takes place in February 1900, 11 months before the Australian colonies federated and 11 years before the creation of the Australian Capital Territory within New South Wales. When Mrs Appleyard addresses the gathered pupils to communicate the merciful deliverance of their classmate Irma, the NSW map behind nearby Miss Lumley clearly shows the existence of the ACT (defined in red).