January 28 - April 15, 2019*

January 28 - April 8

Photoperiod Clues
Every Monday for 11 weeks, sunrise/sunset data will be provided from all 10 sites. Use it to calculate photoperiod.  Then use photoperiod to estimate the latitude of each site.

    March 11 Time Clues
As the spring equinox approaches, time clues will be posted on March 11 to help students estimate the longitude of each site.
March 18 - April 8

Continent, Country, City Clues
During the final 4 weeks, clues will be provided to help you narrow your search from continent, to country, and then to city. Research to pinpoint locations.

  April 15 Mystery Sites Revealed
Locations of the 10 Mystery sites are posted.

* Please note: Due to budget limitations, our spring 2019 Mystery Class challenge will be a replay of a previous year's challenge. We will reveal the locations of the 10 Mystery sites on Monday, April 15, 2019 but will not be able to hold a year-end contest.