What does “[1850]” mean in the Interpretation Act 1978?

Question

In Schedule 1 to the Interpretation Act 1978 there is the line:

“Month” means calendar month. [1850]”

What does 1850 here refer to? And what convention is the notation in?

Answer 1

The line you mention is in Schedule 1.

Schedule 1 includes a note:

Note: The years or dates which follow certain entries in this Schedule are relevant for the purposes of paragraph 4 of Schedule 2 (application to existing enactments).

Paragraph 4 of Schedule 2 says:

paragraphs of Schedule 1 at the end of which a year or date is specified apply, so far as applicable, to Acts passed on or after the date, or after the year, so specified

Answer 2

To add to Jen's answer: where it's just a year in square brackets, this refers to the Interpretation Act passed in the specified year.

As far as I can tell, only two such years appear in the Act, namely 1850 and 1889, which are the years of the two previous such Acts.

Other dates indicate definitions sourced from, or inserted by, other Acts, and hence refer to when the relevant Acts came into force.

This is more obvious on the King's Printer version (the official printed version of the Act when it was first published), which has notes in the margin throughout Schedule 1, listing the Acts of Parliament which inserted or supplied those entries.