doesn't the last sentense says you have to use your own time, in a rather confusing way ?

i use the local time and it works just fine ( +1 hour from greenwich ). I think that doesn't really add up if you use GMT. On the norther hemisfire, the sun is always on the south wenn it's 12 a clock. If you put GMT on your watch and you are in the states or something, at 12 a'clock on your watch the sun will be on the east than ! ( well almost east ).