Sunrise/Sunset changes for January:
Guam:
Jan 1, 2008 6:44 AM 6:05 PM 11h 20m 45s + 0m 09s
Jan 31, 2008 6:49 AM 6:21 PM 11h 32m 21s + 0m 33s
Sunniness increases by 12 minutes
Detroit:
Jan 1, 2008 8:02 AM 5:10 PM 9h 08m 18s + 0m 42s
Jan 31, 2008 7:48 AM 5:44 PM 9h 56m 51s + 2m 17s
Sunniness increases by 48 minutes

Seasons can matter four times as much in Michigan.