Djokovic had another late night underneath the Centre Court roof but made sure he didn't have to stay quite as long as two years ago by wrapping up a 6-4, 6-4, 6-4 victory over Ryan Harrison of the United States in just under two hours.
The top-ranked Serb is in the Wimbledon history books for having won the match with the latest finish ever in a tournament that began in 1877, a five-set victory over Olivier Rochus that finished at 10:59 p.m. in the first round in 2010.
He was tested again by Harrison but showed his sharpness in key moments to eliminate the American just before 10 p.m. local time.
"We went the distance until 10 o'clock in the night and played under the roof. It was a different condition," the defending champion said. "It was a really enjoyable match."
The match had a late starting time as it was the fourth of the day to be played on Centre Court -- instead of the regular three -- as Wimbledon played a bit of catch-up because of rain delays.
Roger Federer needed less than 80 minutes to wrap up an easy win in the first, playing in front of Prince Charles who made his first visit to the tournament since 1970.
Caroline Wozniacki then wasted two match points before losing in three sets to Tamira Paszek of Austria in a first-round match that had been suspended on Tuesday, before Kim Clijsters reached the third round with a 6-3, 6-3 win over Andrea Hlavackova.
So by the time Djokovic was wrapping up his match, there was total darkness outside the Centre Court, where floodlights illuminated the white retractable roof and hundreds of seats were gaping empty as some fans had already gone home.
That didn't take away from the experience for Djokovic though.
"Every time I step on Centre Court you can feel the different energy from any other tournament," he said. "There's a lot of tradition and history and champions who have made history on this court, so I'm trying to enjoy every single moment of it."
The match against Harrison could easily have gone on much longer, as the contest was closer than the score suggests.
Djokovic hit 31 winners to the Americans 30, with 15 unforced errors compared to 14 for Harrison.
The difference came on break points. Djokovic converted all three that he earned, while Harrison went 0-6.
"I played really well from the start to the end, but it was a close match," Djokovic said. "He performed really well when he needed to, but I got the crucial breaks in every set, and that was enough to win."
Federer had a much easier time, beating Fognini 6-1, 6-3, 6-2.
Prince Charles and his wife Camilla, the Duchess of Cornwall, sat in the first row of the Royal Box as Federer walked onto Centre Court for the day's first match.
He and Fognini stood side by side as they bowed awkwardly toward the royals, and Charles responded with a wave and grin.
When Federer completed his victory, Charles and Camilla joined the crowd's applause. He visited with the royal couple afterward for several minutes, talking about tennis, polo and Federer's young twin daughters.
"They were very nice, very sweet and thought I played great," Federer said, "which was very nice to get some compliments after the match, which was unnecessary, but of course I do appreciate it."
Shortly after Federer's victory, rain interrupted play, and the retractable roof on Centre Court was closed for the first time in the tournament.
When play resumed, Wozniacki lost 5-7, 7-6 (4), 6-4 to Paszek, her first opening-round exit in a Grand Slam since the 2007 French Open.
Reigning U.S. Open champion Samantha Stosur also lost, as did 2011 French Open winner Li Na. More than a dozen matches on outside courts were postponed until Thursday.
Top-ranked Maria Sharapova led 7-6 (3), 3-1 when her second-round match against Tsvetana Pironkova was suspended because of darkness. Sharapova saved five set points in the first set.
On Thursday, Serena Williams plays Melinda Czink of Hungary, Rafael Nadal faces Lukas Rosol of the Czech Republic and defending women's champion Petra Kvitova takes on Elena Baltacha of Britain.
Nadal is up last on Centre Court, and with showers predicted for a third straight day, he could find himself playing under the roof just as late as Djokovic.
"It's hard to prepare for that because you play indoor match on the Centre Court maybe once every couple of years," Djokovic said. "The crowd enjoyed it so it was a spectacular match from a player's point of view.
Sometimes it's good for a change to be under the roof. It makes it more interesting as well, if you go to the late hours."