Call me a party pooper, but I did nothing this year to mark Pi Day. I baked neither a sweet nor a savory pie. Perhaps worse, but without deliberate offense to STEM-loving peoples, I also failed to observe Albert Einstein’s birthday that day — no Instagrammed black-hole image or chummy post on Einstein’s official Facebook page wishing him an HBD.

The next day, I sat out the Ides of March. I felt Scroogishly alone as the Internet simmered with activity, the month flashing by in a dazzle of festivities I barely knew existed — National Puppy Day (March 23), National Tolkien Reading Day (March 25) and National Pencil Day (March 30), all of it tucked within National Women’s Month, not to mention National Social Work Month.

Holidays have always been occasion for angst, ambivalence and sometimes, despite everything, genuine celebration. The greeting card industry has long mastered the art of amplifying holidays to tug at our impulses, whether generous or guilty. But the Internet and its social media accomplices have upped the ante, fabricating new holidays and ushering other time-honored rituals, solemn observations and family quarrels into the ether, where they are louder than ever.

Private rituals are now public. Communal events are worldwide. Everyone is invited, and please bring a smartphone.

Some of this leads to a genuine expansion of the holiday spirit. But given the multitude of noteworthy occasions, it’s hard to keep up with all the celebrating.

“Last Thanksgiving, I wasn’t online all day and then I saw that everyone was talking about what they were thankful for, and I hadn’t,” said Melissa Ryan, a director of client services at Trilogy Interactive, a digital strategy firm based in Washington. “I had this sense of guilt, like I should be posting about my gratitude.” After all, Ms. Ryan always posts on National Coffee Day (“I drink a lot of coffee”). And as a “Star Wars” fan, May the Force Be With You Day on May 4 is a big deal. (“For normal people, it’s ‘Star Wars’ Day, that’s funny. But I love ‘Star Wars’ and have a lot of friends who love ‘Star Wars.’”)

In this socially aware holidaysphere, not only are you meant to post an image of your own Passover plate, you’re to scroll through everyone else’s buffet and like it. With all the sharing and hearting, if you don’t hop on the holiday bandwagon, you feel as if you’re violating some kind of invisible social contract.

“There’s always been Thanksgiving and Halloween and Christmas, but suddenly this year, it seemed like there were all these photos of Easter dinner,” said Whitney Joiner, a senior features editor at Hearst Digital Media. “There were people celebrating boozy Easter brunches! It made it seem like Easter was this big national holiday we were all supposed to be celebrating.”

And there’s so much more to celebrate. Sure, some of the latest holidays exist purely in the confines of the cloud. No reasonable person is going to grab the nearest vegan because of Hug a Vegetarian Day. But other “microholidays” or hashtag holidays have crossed over into the real world.

Interactive Feature | NYT Living Newsletter Get lifestyle news from the Style, Travel and Food sections, from the latest trends to news you can use.

Susan McPherson, 51, a corporate responsibility consultant, was invited last year for the first time to a pie party in observation of Pi Day. “There were tons of pies,” she said. “Of course, I posted a picture; the pies were so beautiful.”

Whether they originated as public relations opportunities or alleviators of boredom, these gratuitous celebrations can stir some of the same emotions the old stalwarts do. And just like traditional holidays, the new ones can manage to make you feel full and empty at the same time. “Holidays online can be a wonderful way to feel like you’re not alone in the world,” Ms. McPherson said. “But it can also make you feel like the loneliest person in the world.”

At the same time, social media celebrations can be a boon to the lonesome. “Holidays online are a way for me to take the air out of how lonely it can be,” said Tim Federle, an author and co-writer of the Broadway musical “Tuck Everlasting.” “One Valentine’s Day, I saw a heart-shaped balloon sticking out of a garbage can, and I took a photo and posted it on Facebook with the caption ‘Too soon!’ It got so many likes, it really bolstered me.”

That commiseration now takes place in real time. “It used to be that at some point during holiday festivities, everyone would sneak off and go online and ask, ‘Hey is anyone else there?’” said Clay Shirky, a global network professor at New York University and author of “Here Comes Everybody.” “And it turned out everyone was there. People were done with their families, and had moved on to their adoptive families online. Only now, we don’t have to wait or sneak away any more.”

According to Mr. Shirky, the Internet has a long tradition of embracing minor holidays, starting with April Fools’ Day when, in 1984, a group of Usenet regulars posted a hoax called “Kremvax,” in which the Russians supposedly sent a message from the Kremlin. Since then, holidays have been marked globally as they roll through successive time zones, and meta-holidays like Thanksgiving Clapback (people tweet out their holiday complaints) have blossomed based on existing ones.

In some cases, offline holidays have migrated into the ether. Andrea Schneider, a director of product management at the Internal Revenue Service who lives in Bethesda, Md., recently started observing Rosh Hashana online. She, her husband and their two children curl up on the sofa and stream a service they like at a synagogue in Ohio. “At services around here, I always felt a little lonely without my entire extended family,” Ms. Schneider said. “Watching online with my kids, I feel like I get back some of the feeling of togetherness I was looking for.” Friends of hers have set up a Google Hangout where they light Sabbath candles together.

On the Internet, all are included: distant relatives and friends, elderly aunts and sick grandparents can be virtually drawn into a physical gathering they may otherwise miss. This used to happen post facto, when photographs were mailed; now celebrants keep cellphones by their side throughout dinner, posting images as they eat. But it can take away some of the intimacy and informality.

“A 22-year-old woman complained to me that she used to love coming home for the holidays,” said Sherry Turkle, author of “Reclaiming Conversation: The Power of Talk in a Digital Age.” Once her mother started posting all the photos online, she missed the privacy. “Before, she could relax and be a child again, but now she feels like she has to put on makeup and be on her best behavior. What was once a private affair is now a quasi-public event.”

Jen Nedeau, director of strategic communications at Bully Pulpit Interactive, said, “Social media brings us to a community table where we get to experience holidays in the same room.” As she sees it, social media functions the way Hallmark used to, helping us figure out which holidays matter to us, and fostering communities that mimic the experience of small towns where everyone can digitally laugh together at what Grandma just said.

This all feels so “It’s a Wonderful Life,” it’s hard to sound a curmudgeonly note. I’ve tried to be more festive in April, National Poetry Month, posting several odes to verse. On National Siblings Day (April 10), while everyone else displayed sweet childhood photos of sisters hugging, I went gung-ho on Twitter: “When I was a child, my older brother would pin me down and let long tentacles of saliva dangle menacingly in my face. #HappySiblingsDay.” A bunch of total strangers favorited it, and I felt good.