A calendar is a system of organizing days for social, religious, commercial, or administrative purposes. This is done by giving names to periods of time, typically days, weeks, months, and years. The name given to each day is known as a date. Periods in a calendar (such as years and months) are usually, though not necessarily, synchronized with the cycles of some astronomical phenomenon, such as the cycle of the sun or the moon. Many civilizations and societies have devised a calendar, usually derived from other calendars on which they model their systems, suited to their particular needs.
A calendar is also a physical device (often paper). This is the most common usage of the word. Other similar types of calendars can include computerized systems, which can be set to remind the user of upcoming events and appointments.
Here is the world's most bizarre calendar ever
20 Year Warranty Calendar
This graphical representation of 20 years sticks out from the wall so much, it might be getting in your the way for two decades
T-shirt 2009
Wear this T-shirt calendar, cross off each day of 2009 with its attached pen, and then you can stand it up in the corner for posterity. Deodorant not included.
Ambient Clock
Beyond a mere clock, the Ambient Clock (still in beta) is wirelessly linked to your Google Calendar, changing colors from blue when you’re idle to bright orange when you’re in the middle of a scheduled event.
Antikythera Celestial Machine
Is it a calendar, calculator or ancient computer? Yes. More of a demonstration of planetary and stellar motion than a calendar, this hand-built marvel counts the days and signs of the zodiac on a grand scale.
Bubble Calendar
Got a jones for popping bubble wrap? Mark each day of 2009 with a pop for $30.
Everlasting Adhesive-Tape Calendar
Stick it up anywhere, get organized forever. Match up the roll of days with the roll of dates, and you’re golden. Or, uh, bright day-glo yellow.
Chrono Shredder
Great for those who want to forget the past, shredding each day into oblivion as it passes.
Jenda Lifetime Voice Calendar
Forget typing, just talk to this $40 calendar and it records (and then plays back) your important reminders with a single touch.
LEGO Desktop Calendar
Stack these three LEGO-inspired cubes however you want, and then you can accurately count how many days you wasted attempting to build that $500, 5195-piece Star Wars Millennium Falcon LEGO set.
Calendar Matches
We’ve heard of killing time, but now you can strike a match and burn it, one day at a time.