What's being suggested isn't that unusual and it's a direction many countries are heading towards. I don't support Corbyn or this Labour party but not every suggestion they make is bad, and it will happen sooner or later under one government or another.
"
Most countries in the developed world have seen average hours worked decrease significantly.
[14][15] For example, in the U.S in the late 19th century it was estimated that the average work week was over 60 hours per week.
[16] Today the average hours worked in the U.S. is around 33,
[17] with the average man employed full-time for 8.4 hours per work day, and the average woman employed full-time for 7.9 hours per work day.
[18] The front runners for lowest average weekly work hours are the
Netherlands with 27 hours,
[19] and
France with 30 hours.
[20] In a 2011 report of 26
OECD countries, Germany had the lowest average working hours per week at 25.6 hours.
[21]
The
New Economics Foundation has recommended moving to a 21-hour standard work week to address problems with unemployment, high carbon emissions, low well-being, entrenched inequalities, overworking, family care, and the general lack of free time.
[22][23][24] Actual work week lengths have been falling in the developed world.
[25]
Factors that have contributed to lowering average work hours and increasing
standard of living have been:
Recent articles
[26][27] supporting a
four-day week have argued that reduced work hours would increase consumption and invigorate the economy. However, other articles state that consumption would decrease, which could reduce the environmental impact.
[28][29][30] Other arguments for the four-day week include improvements to workers' level of education (due to having extra time to take classes and courses) and improvements to workers' health (less work-related stress and extra time for exercise). Reduced hours also save money on
day care costs and transportation, which in turn helps the environment with less carbon-related emissions. These benefits increase
workforce productivity on a per-hour basis.
https://en.m.wikipedia.org/wiki/Working_time