Choose 4 days from the calendar that form a square of numbers. Ask someone to sum the numbers of the four days. Using algebra, you can tell what the four days are. See site for more information.

Learn about the ancient Aztec calendar. This work is © by René Voorburg, William Horden and Marta Ramirez.

Site displays current year. Scroll down the site for holidays and observances. Continue scrolling to select calendar for any year: past, present, future. Also scroll down to links to World Clock, Year Countdown and more

History of the development and examples of calendars in many cultures. This exhibit is a public service of the Institute for Dynamic Educational Advancement (IDEA).The primary contributor is Claus Tøndering, based in Denmark.

History and display of calendars. Included are: Christian, Jewish, Islamic, Chinese, Mayan, French, and others.

History of the Leap Year.

Current local time at hundreds of locations around the world. User able to toggle to specific continents. Also have ability to enter current time in one city and obtain date and time at another world site.

Current time AND such information as the current number of marriages, divorces, cancer cases, HIV infections, Births, Deaths, and more. Created by Poodwaddle.com.

WORLDTIME® is a service featuring an interactive world atlas, information on local time as well as sunrise and sunset times in several hundred cities, and a database of public holidays worldwide.

This document will tell you where in PI your birthday first occurs, e.g. if you were born Feb 20th 1969 search for: 22069

Information about mathematicians who were born (or died) on this date in history.

Complete list of birthdays of mathematicians throughout the year. Just click on a given date and the birthdates are displayed for that day.

Listings of mathematical meetings around the world by the month and year of the scheduled meeting. Site maintained by American Mathematics Society (AMS).