One prominent swimming coach called it "irresponsible." Another labeled it a "business decision."
World governing body FINA, meanwhile, placed the onus on the International Olympic Committee.
Whatever the factors at play, the bottom line for swimmers is this: they'll be competing until or after midnight at next year's Olympics in Rio de Janeiro.
Finals will begin at 10 p.m. local time — about four hours later than swimmers are used to. To compensate, what are usually known as "morning" heats will begin at 1 p.m.
"We will prepare for it, but it's a pretty irresponsible decision that has been made," Australia head coach Jacco Verhaeren told The Associated Press.
The schedule will suit the North American television audience with Rio one hour ahead of New York, and four ahead of the U.S. west coast. It also suits Asia, where late-evening events in Rio happen in the morning the next day and may extend into the early afternoon.
Audiences in Europe, however, will be virtually shut out.
"We said no. But it's not us who decides," FINA executive director Cornel Marculescu said before Sunday's end of the world championships, which had a more traditional 9:30 a.m. and 5:30 p.m. schedule. "It's an IOC event and we have to respect it. We have to adapt. ... Television is very important for everybody."
The schedule will be toughest on multi-event swimmers and medalists. After post-race interviews, a news conference and a doping test, competitors might not return to the athletes' village until the early hours of the morning.
"Normally at 2, 3 in the morning in the athletes' village there's a skeleton staff and there's not a lot of (food) choice," said Cameron van der Burgh, the South African hoping to defend his 100-meter breaststroke title in Rio.
FINA is working to ensure that swimmers will be lodged on the top floors in the village to avoid disturbances and let them sleep later than other athletes.
"The quality of food, availability of food, and transportation will be assured," Marculescu said. "And there will be two temporary pools in the village for training. ... We are trying to facilitate as much as possible."
Swimming won't be the only sport with late start times in Rio. Beach volleyball, volleyball and basketball games are also slated to run past midnight.
The swimming schedule brings to mind the morning finals at the 2008 Beijing Games, enabling Michael Phelps' record haul of eight golds to be seen live in prime time on NBC in the United States.
"Who knows what will happen in 2020?" said John Rudd, coach of Lithuanian breaststroke standout Ruta Meilutyte. "At least we know and we're not being told about it six weeks before. Plenty of time to prepare."
"Sport is also a business," Rudd added. "Everyone has to make sensible business decisions as well as sensible athlete decisions and there's a balance there. Whether they got the balance right, that's a matter of opinion. But for this sport to survive we've got to take money where it is."
The U.S. Olympic trials won't be adjusted time-wise to duplicate the schedule in Rio.
"We'll start making adjustments in our training camps the three weeks after Omaha trials," U.S. national team director Frank Busch said. "We'll train later in the morning and train later at night."
The traditional pool events in Rio are scheduled for Aug. 6-13 next year.
"It's an Olympic Games so people will find a way to move times on and break world records and whatever else," Rudd said. "But you can always argue that whatever you're seeing, if we were doing it at the right time of the day you would be seeing something even faster."