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Jim, can you include an example you got using using your calculator, NASA, and Co-Pilot?  Start off with Day, Mo, Year, Hour, Minute, Sec.  convert your local time into UTC or ZD 0 time zone.   Don't use daylight savings for your local time.  Then show the "Julian Date" format output by the 3 solutions.  I'm grasping at straws, but could Co-Pilot be outputting Terrestial Time and using TT in it's calculations?  As I think of it, TT builds on top of Julian Date and Time.  I'm sure someone can describe the difference between these 2 time scales.

Also consider reading Jean Meeus book that I replied earlier about.  You don't have to read the entire book.  Just the chapters you are interested in...Julian Date, Terrestial Time, Sun Position.  The nice feature of Meeus' book is that you can first read a chapter in the middle of the book, and he'll reference earlier chapters that you need to know about to understand that chapter you are reading.  You can do a google search and find PDF copies of his book.  The other nice feature of his book is that it contains examples with his answers.  If you do his questions and get his answers, you got a debugged program.

I hope I'm being helpful.  It is hard for me to tell you what the problem is when I haven't tried to use co-pilot.