Bug in sunrise/sunset program

[BEATTIE]

> 
> 	Has anyone else had trouble with Robert Bond's sunrise/sunset
> calculation program? 
I tried to understand the various arguments, like -t to change the time.
What does the current time have to do with when the sun rises??

I got out my almanac and it says that on January 1,1981 the sun rose at
06:36 GMT and set at 17:32 GMT,
so I tried sun -z 0 -a 51.5 -o 0 -d 01/01/1981
it says the sun rises at 08:06 and sets at 16:02.
What is the problem?
Tom.