The 31st carries two things at once. It is the deadline for filing a self-assessment tax return on paper — three months earlier than the online deadline of 31 January — and it is Halloween, which has grown from a minor import into one of the busiest evenings of the British autumn.
The 31 days of October 2030 contain no bank holiday in any part of the United Kingdom, so the working-day count is set entirely by the weekends. It is also the month containing the longest day of the year in clock terms: the Sunday the hour goes back runs to twenty-five hours.
October 2030 closes on Halloween with the clocks already back and the evenings collapsing inwards. November follows with Bonfire Night five days later, Remembrance on the 11th and the Sunday nearest it, and St Andrew's Day at the end for Scotland.