This solar calendar is a modified version of the one at PVEducation.org. The changes are primarily to allow input of local time rather than UTC but also include enhanced data entry validation and convenience features including;
1) Support for local time entry and specification of Daylight Savings Time
2) Display of sunrise and sunset in local time. The results in sunrise and sunset values compare within 3-5 minutes of those calculated by the NOAA Sunrise/Sunset Calculator
3) Ability to switch between latitude/longitude entry in decimal degrees or degrees, minutes, and seconds as well as the ability to choose a world city.
4) Automatic calculation of the time zone based upon the input longitude with the ability to manually over-ride the time zone or eastern longitude for cases where the location is not in the "proper" time zone (for example Boston or Quebec City, which are both east of the Eastern Time zone boundary)
5) Explicit identification of hemispheres to avoid confusion about positive and negative latitude and longitude
6) Validation on all data fields and display of error message when invalid entries have been made (i.e. latitude < 0 or > 90)
7) Modified styling to handle older IE browsers and make output/calculated values more obvious by using spans rather than input boxes. Background also flashes between "day" and "night".
Another useful link is the Navy calculator of daylengths which can be used to help calculate % total sunshine received if the recorded sunshine hours are available.
Charles Landau has a site which provides information on the optimal tilt for a solar panel.