The keys to Pirelli's coveted calendar: saucily-underdressed models and exclusivity.
The hype surrounding the calendar is partly due to the fact that only a select few can get their hands on an actual hardcopy. The Italian tyre-maker has been publishing "the cal", as it is affectionately known , since 1964 and distributing it to a select group of customers.
This year, the calendar made headlines again because it was announced that no nudes would be featured for the first time in its history.
Here are seven things about the most famous girlie calendar in the world.
1. 42 editions since 1964
Originally started as a marketing tool, Italian tyre-maker Pirelli's annual calendar quickly became a cultural icon, well-known for its artfully shot nudes of the world's most famous and beautiful women.
Although 51 years have passed since its first edition was published in 1964, only 42 calendars have ever been produced. This is because the calendar stopped publication from 1975 to 1983 as a result of the oil crisis in 1973.
The latest edition is shot by legendary photographer Annie Leibovitz. Her second assignment for the calendar features 13 "women of achievement", including American tennis star Serena Williams, comedian Amy Schumer and singer-songwriter Patti Smith.
2. Not just for fashion and art photographers
This year's no-nudes calendar is not the first time it has tried something different. In 2013, Pirelli commissioned famous war photographer Steve McCurry to shoot in Rio de Janeiro, producing stunning images of 11 supermodels, including Adriana Lima, in the gritty streets of the Brazilian city.
3. Calendar men too
Although more well-known for featuring gorgeous, scantily-clad women, the 1998 edition paired female subjects with famous men, including actors Ewan McGregor and John Malkovich, as well as U2's Bono.
4. Leibovitz's first nude shoot
The 2000 Pirelli Calendar was the first time Annie Leibovitz photographed nudes. It resulted in stunning images which imitate art more than the usually racy nudes that fill the Cal. The photographer chose the classic nudes of Rubens and Botticelli as her inspiration for the shoot, resulting in raw, untouched images of the female form.
5. No age limit for a Pirelli girl
It seems the Pirelli Calendar is not averse to featuring beautiful women of varying ages. Four older women have made it to the Cal: Besides Patti Smith, 68, in the latest edition, the others are artist Yoko Ono, 82, art patron Agnes Gund, 77, and the legendary Italian beauty Sophia Loren, who made her Pirelli debut at the grand age of 72 in the 2007 edition.
6. Famous supermodels take it all off
Among the most famous supermodels who have bared it all for the Cal are a 19-year-old Kate Moss, shot with just a string of beads draped around her neck by American fashion photographer Herb Ritts in the Bahamas in 1994.
Others who have stripped for the calendar include Naomi Campbell in 1995, Milla Jovovich in 2006 and Adriana Lima in 2015.
7. A missing 1963 edition?
Rumous online hint to the existence of a 1963 edition which was either never published or was so terribly mundane it was wiped from the Pirelli history pages. It is said Terence Donovan, an emerging British photographer at the time who would later shoot the 1984 edition with Naomi Campbell, was behind the photoshoot.