Calendar of Patent and Trademark
- U.S. Trademark office offers a trivia calendar showing famous patents sorted by month of invention.
- http://www.uspto.gov/web/offices/ac/ahrpa/opa/kids/calendar/

Today's Date
- Today's date from the Gregorian calendar that we use into the calendar dates of the Mayan, French, Islamic, Hebrew, Julian, Ethiopic, Coptic, Chinese, Julian, and Discordian calendars.
- http://isotropic.org/date/

Counting: Calendars and Cords
- A look at the methods ancient civilizations used to keep track of time.
- http://www.classzone.com/net_explorations/U4/U4_main.cfm

Several Calendars
- Learn some basic information about the Egyptian, Roman, Gregorian, Mayan, Islamic, Jewish, and Julian calendars. Also learn how to calculate Easter.
- http://www.ortelius.de/kalender/idx_en.php

Royal Observatory at Greenwich - Leap Years
- Learn why we have leap years.
- http://www.nmm.ac.uk/server/show/conWebDoc.349

Indian Moons
- A list of many American Indian tribe's names for months, days, and other calendar related information.
- http://americanindian.net/moons.html

Western-Chinese Calendar Converter
- Tool to convert between the traditional Chinese lunar calendar and the Western solar calendar. Also offers a brief description of the two different calendars and lists links about the Chinese calendar.
- http://www.mandarintools.com/calconv_old.html

Date Algorithms
- Provides descriptions, proofs and computer programming implementation examples to convert dates to various calendar dates for Julian, Gregorian, and Rata Die calendars.
- http://vsg.cape.com/~pbaum/date/date0.htm

Calendar Studies
- Articles on the Gregorian and Julian calendars, the ISO date format, the Julian day number system, the Maya calendar, the Goddess lunar calendar, the Liberalia Triday Calendar and C functions for date conversion; plus software for calendrical conversion.
- http://www.hermetic.ch/cal_stud.htm

Japanese Calendar
- Converts Japanese to Western calendar dates.
- http://www.artelino.com/articles/japanese_calendar.asp

The Ancient Calendar
- The ancient calendar, its origin, problems, and development, plus a look at the names of days of the week
- http://ancienthistory.about.com/library/weekly/aa100797.htm

History of the Calendar
- How different parts of the world made different kinds of clocks based on where they lived and what kind of weather they had to predict.
- http://www.infoplease.com/ipa/A0002061.html

Cosmic Calendar
- Imagine if the history of the universe, all 13 billion years of it, were put into just one year. What would that calendar look like? Carl Sagan, the famous astronomer, made this one.
- http://school.discovery.com/schooladventures/universe/itsawesome/cosmiccalendar/page2.html

Years
- How a year is figured and who invented our calendar.
- http://www.mrdowling.com/601-years.html

Algebra - Fun with Calendars
- Perform some mental "magic" tricks based on math and the calendar.
- http://math.rice.edu/~lanius/Lessons/calen.html

Leap Year
- The Forest Preserve District of Cook County Illinois explains leap year.
- http://www.newton.dep.anl.gov/natbltn/700-799/nb745.htm

Calendars Through the Ages
- Discusses currently used and unused calendars such as Chinese, Christian, Indian, Islamic, Jewish, Ethiopian, Balinese, Bahai, the French, Mayan, Roman, and some modern schemes for calendar reform. Includes timelines and all about how our week came into b
- http://webexhibits.org/calendars/index.html

TimeandDate.com: Calendar
- All 12 months, plus lunar phases and some holidays noted.
- http://www.timeanddate.com/calendar/

Zoroastrian Religious Calendar
- Three versions of the Zoroastrian calendar from the most ancient to more modern calendars.
- http://www.avesta.org/zcal.html

Virtual Perpetual Calendars
- Lets you know what any calendar looks like for the 20th and 21st centuries. Also includes holidays, leap years, which years a particular day of the week always falls on, and methods of calculation.
- http://www.vpcalendar.net/

The Moon's Phase
- Online calculator that lets you see which phase the moon is in for any date in any year.
- http://imagiware.com/astro/moon.cgi

Religious Calendars and Holy Days
- Explanations of the Christian, Jewish, Muslim, Hindu, Buddhist, Sikh, Bahai, and Wiccan calendars. Also includes a list of holidays associated with these calendars.
- http://www.religioustolerance.org/main_day.htm

The French Revolutionary Calendar
- Convert any date since 1792 to the Jacobin calendar, a calendar that came out of the French Revolution but was ultimately not permanently adopted.
- http://www.windhorst.org/calendar/

Ethiopian Calendar
- Discusses which calendar Ethiopia uses and gives a list of the month's names and public holidays in Ethiopia.
- http://ethio.com/calendar.html

Aztec Calendar
- Shows you the current date according to the sacred Aztec calendar. Gives a reading of the significance of the day and the relevant gods.
- http://www.azteccalendar.com/