I worked a four and half day week thirty years ago. As far as I'm aware it's always been quite common for manufacturing companies to do this but that is misleading as we still worked the same hours as a five day week, just four longer days. It seems to be that the Labour plan is more about hours than days.
"The next Labour government will reduce the average full-time working week to 32 hours within the next decade," he said.
As an outsider looking in, this looks like a reasonable aim. I have posted before about one of the founders of my last school who was a leader in the movement
""persuading 300 or 400 of the leading merchant princes of Manchester to allow the clerks and warehousemen to have a half holiday without any reduction in pay."
which other towns and cities soon followed. We don't now believe we should only have Sundays off or that people should work from six in the morning 'till 10 at night. The world did not collapse with this reduction of working hours or with a further reductions.
No one , but no one, is suggesting that this would happen immediately.
It was Keynes who famously predicted that by 2030 we would (or perhaps should?) all be working 15-hour working weeks. He argued that the nature of industrial development was such that ever more efficient and productive technologies would reduce necessary labour time while providing abundance for all. The main thrust of Keynes’s argument makes sense: with each gain in productivity we could have worked less, enjoyed more leisure and let our machines take on more of the hard graft. Tragically, what actually happened is that once the age of full employment, high productivity and high wages was ended by the neoliberal consensus of the early 1980s, the dream of an even shorter working week became exactly that. (Guardian Thu 12 Sep 2019)
If we want everyone to benefit from the progress in technology, it's certainly something which needs exploring.