ICC chief executive Dave Richardson said the move came because of a "question mark" over test cricket's sustainability.
"We have to trial these things as a result. Is four-day cricket going to provide a better product? Who knows, but we've taken similar approaches to the introduction of technology and pink-ball tests.
"At the cricket committee [an ICC arm consisting of some of the game's luminaries], cricketers are traditionally traditional and the majority are reluctant and skeptical as to whether four-dayers are a good thing.
"But there's an acknowledgement we need to do something. Maybe this will be the catalyst to create interest in countries where test cricket is diminishing."
The general view is that four-dayers will help with scheduling across a given week and reduce costs although, as Richardson pointed out, Lord's and other popular test venues see fifth days as a licence to profit.
New Zealand Cricket's preference is to continue with the status quo.
"That is the pinnacle," chairman Greg Barclay said. "But we recognise four-day tests are a good trial and those countries developing as full members [such as test championship absentees Zimbabwe, Afghanistan and Ireland] lend themselves to four-day tests for cost and time reasons.
"Perhaps tests are not supported to the extent they have been by fans or broadcasters - who are not as keen on it as a commercial proposition. This is probably the shot in the arm the game needs.
"Getting context and relevance around the test game will help."
Tactics and pitch deterioration also need consideration should five days meld into four.
"Captains will have to approach the game differently," Richardson said.
"Five-dayers are a test of staying power. Often they're won by the team that goes to the ground fighting fit on the fifth day. Four-day tests will level the playing field.
"Stronger teams might need to use innovations such as declaring their first innings earlier, rather than batting to 500-600, to ensure there is time to win the game. It might produce more attacking cricket."
The test championship has been supplemented by a 13-nation one-day international league which will run every three years (but two initially from 2020 as ICC contracts with sponsors and broadcasters are worked out).
The league will provide a direct qualification pathway towards the World Cup for the 12 full member countries and the winners of the next tier's world league championship.
The onus goes on administrators to work towards another Future Tours Programme deadline by the end of the year to set schedules until 2023. Those are expected to be presented and actioned at the next meeting in February.
The resumption of tours to Pakistan, in limited overs cricket initially, are also a step closer after the success of the World XI series security arrangements in Lahore.
"Pakistan security agencies have done lot of work in lowering the threat [of terrorism]," Richardson said.
"The risks are still significantly high, but the plans produced for the World XI series were strict and unprecedented.
"The people implementing them could do so 100 per cent, whereas they often look good on paper but fall apart. It's all about increasing the confidence in players and teams."
