Hizzoner doesn’t know how to honor time.

New York City mayor Bill de Blasio apparently ran late for his own wedding. That’s according to Sal Albanese, a former city council member running against the incumbent to be the Democratic nominee for mayor. Albanese was present at the mayor’s 1994 nuptials to Chirlane McCray, and recalls sweltering under the hot summer sun while waiting for de Blasio to get hitched.

That was just an early instance of the mayor’s famous tardiness. In 2014, he famously turned up late for a memorial service commemorating air crash victims, and has left everyone from Italian villagers from his ancestral home to NY Senator Chuck Schumer hanging. By some accounts, de Blasio has gotten better at being on time, but his reputation still precedes him.

While punctuality can be culture dependent, chronic lateness is still frowned upon in most corporate contexts. “In North America, being on time means being on time. There’s no such thing as being fashionably late,” says etiquette expert Julie Blais Comeau. “Being late sends out the unconscious message that ‘my time is more valuable than yours,’” she adds. “That’s disrespectful and affects productivity and morale.”

If for some reason you do happen to be running behind, the author of “Etiquette: Confidence and Credibility” recommends informing the parties waiting for you as soon as possible. “If you’re late for a nine a.m. meeting, you usually know by eight thirty,” she says. And if the meeting is one that’s face-to-face and one-on-one, you really should phone the person.

Apologies are probably de rigeur when you’re late, but be careful not to overuse them. “When people ‘apologize’ they usually aren’t really that sorry,” says executive coach Debra Benton. “It’s required for social balance and using it once is believable. But if they were sorry for being late, they wouldn’t be late.” That’s why you should have a solution in hand when you call in to let others know you’ve been delayed. Blais Comeau recommends either encouraging the meeting to start without you—if your presence isn’t key—or going somewhere quiet and phoning in to the meeting via phone.

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The situation however, becomes a tad stickier if you work for someone who’s always late. Experts say if it’s clear that many people are being affected, someone should go up to the manager while they’re not busy and explain the consequences. “Ask how to prevent it in the future and then take offensive action to make sure they’re on time,” says Benton, co-author of “The Leadership Mind Switch.” This may include telling perpetual latecomers that meetings start 15 minutes earlier than actually scheduled, or setting them at unusual times like 10:03 a.m. so that you get their attention.

If all else fails, punish the latecomer—but with good humor. One trick Blais Comeau has utilized is “ceremoniously passing” a tablet with meeting minutes to the last person who’s walked into the door and designating them as the note keeper. “You don’t want that to happen” to you, so you’ll be encouraged to come early, she says. And as an added benefit, the person will have access to all the notes written beforehand. “They’re not going to stop the meeting, because they no longer have to ask what they missed,” she says.