See also:

• Kids and Teens: School Time: Science: Astronomy and Space: Time  (25)

Algebra - Fun with Calendars - [ Teens/Mature Teens ] - Perform some mental "magic" tricks based on math and the calendar.

The Ancient Calendar - [ Kids/Teens ] - The ancient calendar, its origin, problems, and development, plus a look at the names of days of the wee.

Aztec Calendar - [ Teens/Mature Teens ] - Shows you the current date according to the sacred Aztec calendar. Gives a reading of the significance of the day and the relevant gods.

Calendar of Patent and Trademark - [ Teens/Mature Teens ] - U.S. Trademark office offers a trivia calendar showing famous patents sorted by month of invention.

Calendar Studies - [ Teens/Mature Teens ] - 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.

Calendars Through the Ages - [ Teens/Mature Teens ] - 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 being.

Calendopaedia - [ Teens/Mature Teens ] - All about calendars, different kinds, astronomical time, and how years are counted.

Cosmic Calendar - [ Teens/Mature Teens ] - 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.

Counting: Calendars and Cords - [ Kids/Teens/Mature Teens ] - A look at the methods ancient civilizations used to keep track of time.

Ethiopian Calendar - [ Teens/Mature Teens ] - Discusses which calendar Ethiopia uses and gives a list of the month's names and public holidays in Ethiopia.

The French Revolutionary Calendar - [ Teens/Mature Teens ] - Convert any date since 1792 to the Jacobin calendar, a calendar that came out of the French Revolution but was ultimately not permanently adopted.

History of the Calendar - [ Teens/Mature Teens ] - 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.

Indian Moons - [ Kids/Teens/Mature Teens ] - A list of many American Indian tribe's names for months, days, and other calendar related information.

Japanese Calendar - [ Kids/Teens/Mature Teens ] - Converts Japanese to Western calendar dates.

Leap Year - [ Teens/Mature Teens ] - The Forest Preserve District of Cook County Illinois explains leap year.

The Moon's Phase - [ Kids/Teens/Mature Teens ] - Online calculator that lets you see which phase the moon is in for any date in any year.

Religious Calendars and Holy Days - [ Teens/Mature Teens ] - Explanations of the Christian, Jewish, Muslim, Hindu, Buddhist, Sikh, Bahai, and Wiccan calendars. Also includes a list of holidays associated with these calendars.

Royal Observatory at Greenwich - Leap Years - [ Kids/Teens/Mature Teens ] - Learn why we have leap years.

Several Calendars - [ Teens/Mature Teens ] - Learn some basic information about the Egyptian, Roman, Gregorian, Mayan, Islamic, Jewish, and Julian calendars. Also learn how to calculate Easter.

TimeandDate.com: Calendar - [ Kids/Teens/Mature Teens ] - All 12 months, plus lunar phases and some holidays noted.

Today's Date - [ Kids/Teens/Mature Teens ] - 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.

Virtual Perpetual Calendars - [ Teens/Mature Teens ] - 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.

Western-Chinese Calendar Converter - [ Teens/Mature Teens ] - 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.

Years - [ Kids/Teens/Mature Teens ] - How a year is figured and who invented our calendar.

Zoroastrian Religious Calendar - [ Teens/Mature Teens ] - Three versions of the Zoroastrian calendar from the most ancient to more modern calendars.