Discussion of Challenge Question #2
The "Plot" Thickens:

A sudden and mysterious change happened last week, as the sunrise/sunset times for Mystery Class #9 unexpectedly moved backwards (earlier) by a whole hour. What caused this change to occur? Why didn't the photoperiod also change?

Students from Florida, Illinois, Minnesota, North Carolina,New Jersey, Texas, South Carolina shifted into gear to answer those questions.

And a few classes below went above and beyond, hypothesizing that the time shift might reveal even more about Class #9's seasons and location. Here are just few answers that were very helpful:

Students from John Paul II Homeschool Academy in Minnesota:
This week's sunrise/sunset times for Mystery Class #9 both were different by about an hour from last week. The photoperiod was similar to previous weeks. Our best guess about why this occurred is that the area where the Mystery Class is located must have had a time change. When we investigated this possibility, we found that not everyone has a time change on the same weekend as the United States (Daylight Savings Time). (We have a feeling we know what country has a time change in February, but we don't want to give any clues.) ;-) The photoperiod trend line isn't affected because both the sunrise and sunset times changed, but the amount of daylight is about the same. In other words, the amount of daylight stayed constant; how it is tracked changed.

Ms. Min's class, from Beardsley Middle School in Crystal Lake, IL:
Mystery class #9 experienced a time change. Since they are heading into winter they "fell back" one hour.

Mrs. Greenstein's Fourth Graders from New Jersey:
Class 9's photoperiod changed a whole hour because they had daylight savings. It didn't change the photoperiod because the sunrise and sunset both went back an hour. We think that this class is in the middle of their Fall season. Therefore they must be in the Southern hemisphere

Isabella, a 4th grade homeschool student from Houston, Texas explained:
Mystery Class #9 is experiencing daylight savings time. It doesn't change the photoperiod trend, because it's not changing the length of the time the sun is up, it's just making you set your clocks earlier.

Aaron, a 4th Grader from Agape Academy in Cedar Hill, TX wrote:
The sunrise and sunset are about an hour earlier than the previous week. They must have had some type of Day Light Saving Time, like we do, just about a month earlier. The period of sunlight doesn't change just because we adjust our clocks.