Before a (pink) ball was even delivered in the historic day-night Test at Adelaide Oval, the concept received a tremendous boost. It came in the form of a positive response from Indian captain Virat Kohli. "Hopefully it will be better for the game," said Kohli. "It will be a step that we all might remember a few years down the line. Let's hope so."Apart from Kohli's endorsement, the other major reaction to the arrival of day-night Test cricket has been a renewed call for matches of four days' duration. That suggestion may seem like an extension of the current revolution but it's actually a return to the past, when four-day Tests were a regular occurrence.There's no doubt that what appears to be a successful transition to day-night Tests will make the four-day concept far more practical.Back in 1978-1979, World Series Cricket played day-night Super Tests seven hours a day, running for four days.However, not every international venue can accommodate night cricket and this makes a unilateral move to four-day Tests difficult. This is especially so when Tests continue to move at the pace of the recently completed Perth match between Australia and New Zealand.The overs in Perth were bowled at tortoise speed and the umpires and referee did nothing to move the game along. Batsmen regularly held up bowlers ready to deliver and drinks were served more often than at an office Christmas party.If you throw in time wasted on pointless replays to decide whether a shot was a boundary, the game resembled the phrase applied by comic genius Robin Williams: "baseball on Valium".Among the suggestions to support four-day Tests was one proposing the lifting of the minimum number of overs in a day, from 90 to 100.If four-day Tests are to be a part of the calendar, officials and players will have to speed up the game. Among the avenues available to administrators are full sightscreens with no advertising and a law where it's a boundary if the ball hits the rope.It was noticeable that the pace of play picked up dramatically in the cooler conditions of the inaugural day-night Adelaide Test after the tardiness in the heat of Perth. At the same time as this was taking place, Kohli led India to victory over South Africa well inside three days.Two Tests, one a day-night experiment and the other a short traditional match, were proof that both concepts are feasible. ESPNCricinfo..