But while scribbling in those dates of celebration (Susie's birthday) or more mundane reminders (get oil changed), consider this: there's hardly a day out of the whole 365, it seems, that hasn't been proclaimed "special" in some way, by someone, somewhere.
From World Day of Peace (Jan. 1) to World Sparrow Day (March 20) to Darwin Day (his birthday, Feb. 12) and Autistic Pride Day (June 18), the calendar is littered with celebrations and fundraising opportunities for a seemingly endless list of interests and causes.
So just how do these days come about? And who decides that a certain 24-hour block of time becomes an annual day to remember?
Well, that depends.
The United Nations has designated a slew of days throughout the year as worthy of note, but they aren't just picked willy-nilly and plunked down on the calendar.
Indeed, any day on the UN's list has come about by resolution, typically introduced by a member country or group of countries and presented to the General Assembly, says Farhan Haq, a spokesman for the office of the Secretary General.
SEE: A look at some "special" days in 2013. Story continues below:
"It's actually fairly simple that a member state, any member state, can propose establishing a day, and then they'll just vote on the resolution. If the majority carries on a resolution, then a date can be inscribed into the calendar."
The new year starts out on a bit of a sombre note, with Jan. 27 set aside for the International Day of Commemoration in memory of the victims of the Holocaust.
June 15 marks World Elder Abuse Awareness Day, Aug. 29 is International Day Against Nuclear Tests, Sept. 16 has been declared International Day for the Preservation of the Ozone Layer and Dec. 9 helps close out the year on a political/legal note with International Anti-Corruption Day.
All pretty serious stuff.
And then there are myriad days declared by UN bodies like the World Health Organization and UNESCO, among them World Poetry Day (March 21), World Migratory Bird Day (May 12-13), World Hepatitis Day (July 28) and World Teachers' Day (Oct. 5).
One of the bright spots on the calendar falls on March 20, with the UN's International Day of Happiness.
Some dates end up getting celebrated just because someone or a group of someones thought it would be a cool idea — and the concept spread.
That's the case with Pi Day, which commemorates the mathematical constant 3.14 (ad infinitum) on March 14 (3/14).
Pi Day was inaugurated in 1988 by Larry Shaw at the Exploratorium in San Francisco, where he worked as a physicist before his retirement.
"Larry has a wonderful, quirky sense, and he realized that March 14 was 3/14, and we could celebrate the transcendental number pi," says Ron Hipschman, an educator at Exploratorium. "Then his daughter realized it was also Einstein's birthday."
Pi, which expresses the ratio of the circumference to the diameter of a circle, is an irrational number approximated by Archimedes and other mathematicians going back more than two thousand years ago.
For scientists of all stripes who deal with formulas, pi has an almost magical power. It has an infinite number of digits that never repeat in any kind of pattern. Computer calculations so far have taken it out to about 30 trillion digits and counting.
"The normal way we celebrate Pi Day is we do all kinds of pi- and circular-related events at the Exploratorium," says Hipschman, who helps co-ordinate the day's activities. Over the years, those events have included pizza-pie tossing contests, pie fights and pi digit memorization recitals, as in 3.14159 ... and onwards.
A Pi Shrine was built at the top of a cylindrical building on the grounds of the interactive science museum and a brass plaque was installed honouring the number.
"At 1:59, we have a pi procession where everybody carries a digital pi on a pie plate attached to a beater stick through the Exploratorium, up to the Pi Shrine, where we circumambulate the Pi Shrine 3.14 times while singing 'Happy Birthday' to Albert Einstein," he says.
"And then we eat pie!"
2013 marks the 25th anniversary of the first Pi Day. But San Francisco won't be the only location where people pay homage to the life of pi, Hipschman says.
"It's international now, it's all over the world."
Other days with a scientific theme include: Star Wars Day (May 4), in which fans honour the George Lucas films; Geek Pride Day (May 25), which falls on the anniversary of the release of the first "Star Wars" movie in 1977; and Astronomy Day, a bit of a moving target from year to year as it occurs on a Saturday between mid-April and mid-May, on or just before the first quarter moon.
Pick a topic and there is probably a date to immortalize it, no matter how off-beat or quirky it may seem. Take, for instance, Worldday of Snowman (Jan. 18), World Puppetry Day (March 21), Ballpoint Pen Day (June 10), International Kissing Day (July 6), and — wait for it — International Talk Like a Pirate Day (Sept. 19).
The latter was inaugurated as a joke in 1995 by John Baur (Ol' Chumbucket) and Mark Summers (Cap'n Slappy) of Oregon. The "Arrr!" day gained an international following after the two buddies sent a letter about their all-things-pirate observance ("Ahoy, matey") to U.S. humorist Dave Barry in 2002, who wrote about it in his syndicated newspaper column.
Such red-letter days are often promulgated by governments, organizations and even individuals to laud a group or event or to raise public awareness of an issue.
Among them is Blasphemy Day (Sept. 30), which isn't — as it sounds — about people going around insulting God or showing irreverence for sacred practices.
"People thought we were celebrating blasphemy for its own sake, encouraging people to be as obnoxious as they could be," say Justin Trottier of Toronto, founder of the Centre for Inquiry (CFI) Canada.
In fact, Blasphemy Day is intended to support freedom of expression by encouraging individuals to openly criticize religion without fear of reprisal — a right not afforded people in many parts of the world.
The day was proclaimed by the U.S.-based CFI in 2009 to coincide with the anniversary of a Danish newspaper's publication of satirical drawings of the Islamic prophet Muhammad. Those cartoons set off a firestorm of protests among Muslims worldwide, leading to widespread violence.
"So the Centre for Inquiry decided that a good response would be to remind the public why free speech is important," Trottier, an atheist who champions the separation of church and state, says of Blasphemy Day.
"Within a year we did go back and make some tweaks so it was very clear what our message was ... (and not that) we were just trying to cause trouble," he says.
"So we changed it to International Blasphemy Rights Day. The difference is critical because what we're saying is people should have the right, if they so choose, to express themselves even with satire, mockery or, yes, blasphemy."
All in all, notable days on the calendar cover pretty well every topic area, whether animal (International Cat Day, Aug. 8), mineral (International Mountain Day, Dec. 11) or vegetable (International Beer Day, Aug. 5 — OK, so it's a stretch, but barley and hops are vegetable matter).
And speaking of ingestibles and edibles, days touting various foods are scattered throughout the calendar year, from the UN's World Food Day (Oct. 16) to World Pasta Day (Oct. 25), declared at the World Pasta Congress in Rome in 1995.
Then there are the more dubious "days" dedicated to various food products (read promotion). More than 175 such days are U.S.-based, among themNational Pizza Day (Feb. 9), not to be confused with National Cheese Pizza Day (Sept. 5); National Grilled Cheese Sandwich Day (April 12); National Walnut Day (May 17); and National Catfish Day on June 25, designated in 1987 by then-president Ronald Reagan.
The cork pops on National Champagne Day on, of course, Dec. 31.
Haq of the UN says the names of some days may seem humorous at first glance, but they can represent serious issues with widespread implications.
"For example, some of the days people think are somewhat worthy of jokes, like World Toilet Day. People tend to mock that," he says.
"But in different Third World countries, it's actually an occasion which can allow us both to educate people about the importance of sanitation and clean water, which is a very important health issue.
"Also it can help get different governments to make more commitments to improve their own sorts of infrastructure and provision of sanitation, so that you have a little bit of an impetus for things that otherwise would be forgotten."
And it should be mentioned that paying tribute to such a vast array of interests, pursuits and remembrances as part of the almanac doesn't stop with midnight-to-midnight chunks of time: there are also all manner of weeks, months and even decades that have been ordained as celebratory in some way.
And in case you're wondering, that goes for years, too. The UN has christened 2013 as the International Year of Water Co-operation and of Quinoa — the latter a shout-out to the super-nutritious seed.
Bolivia and several other South and Central American countries proposed that quinoa (pronounced keen-wah) be recognized because of the contribution the ancient Andean crop makes to world food stores.
"It's designed both to build appreciation for that, but also to inaugurate a range of projects that can help to ensure that quinoa cultivation is encouraged in the nations that produce it," explains Haq.
As with any day, month or year decreed significant, "the purpose is to foster awareness of a range of topics that the United Nations believes are valuable for the governments, the peoples of the world to focus on and consider."