Long back, in 2012, I did a very interesting teaching project with primary school children. I also wrote about it in this blog. The same blog article, with some modifications, has been published in Resonance.
Click here for the article (pdf): Discovering Facts: Finding the longest day with school children
For some reasons, there were three footnotes in my article submissions which have been ommitted in the final version. The footnotes were numerically referenced as , ,  in the text but what exactly those are got missed out in the final version (my fault to have missed it at the stage of proof). I am posting those below here:
 Disclosure: The school is founded by close relatives and friends. You can learn more about it by visiting the website: www.purnapramati.in
 A preliminary version of this article appeared in the souvenir of the school in Jan 2013 and has also been put up on my personal/lab blog.
 Data for sunrise and sunset for most cities can be downloaded from: http://aa.usno.navy.mil/data/docs/RS_OneYear.php (you need to know Longitude and Latitute of the place) OR http://www.timeanddate.com/worldclock/astronomy.html?n=438