The reasons given include ease of planning, on a Thursday-Sunday timeframe, then three days off, then do it again; to moving towards more adventurous cricket; to promoting bigger crowds which in most parts of the world are slipping for test cricket.
Generally cricket is pretty adventurous anyway. Call that the modern age where many people have the attention span of a fly.
The longest test, by the way, took place in 1939 at Durban.
England and South Africa played on March 3, 4, 6, 7, 8, 9, 10, 13 and 14, with two rest days thrown in. It ended with England on 654 for five, just 42 runs short of victory, and only because the English party had to get a train for a 1600km trip to Cape Town in time to catch a boat home.
How's that for a fun-filled couple of weeks. Now five days can seem a stretch, unless you are a lover of the long form.
Cricket South Africa need the approval of the International Cricket Council, which has its next meeting in Auckland early next month.
What might the ICC do?
Option one: Tell South Africa and Zimbabwe, who have mutually agreed to the idea, to sit back down and play a five-test test, while pushing the hurry up button on a decision, recognising teams are getting restless.
Option two: Let them get on with it. They are showing some initiative. The world is unlikely to stop with a four-day test. It's not as if all other test nations will immediately follow the African lead. Ashes tests trimmed a day late this year? Doubt that. England in New Zealand in March? Uh-uh.
There is an element of novelty about it. It might also do the ICC a favour, as it would offer a test case for what might lie ahead.
Those opposed to four-day tests have an understandable concern that if one day is washed out suddenly you're down to three days, and getting a result in that time isn't easy, unless you get a walkover.
Provision can be made for an extra couple of hours play each day, utilising lights if needed to try and maximise the available time. These are decisions which can be made between the two teams before the match starts. It doesn't actually need a stamp from the ICC. A bit of commonsense can do the job.
When the ICC come to discuss implementing into law four-day tests, if they are concerned about the impact, they can always suggest a two-year trial period. See how it pans out. There would be enough tests in all parts of the cricket world to get some decent anecdotal information.
This might not actually be a substantial gamble. You would fancy South Africa to win in four days at this stage.
Ponder this. Over the past four decades, there has been a gradual decrease in the number of tests going into a fifth day. More than three quarters (77.1 per cent) of tests in the 1980s went into day five, but that figure has dropped to just 58.3 per cent this decade.
That said, half of last year's tests which produced a winner, did so on the fifth day.
Numbers, schnumbers. All food for thought.
In the meantime, give South Africa and Zimbabwe their chance. Both teams are happy. There's nothing to lose.
