I would say mornings are the best time to submit to digg. This way you have the entire day to gain some diggs back and have people see your link.
Mornings are good. May I suggest quickly sending the link to friends right after you submit it. If you get a small amount of diggs in a short amount of time, it can put you smack on the front page.
I think it's better to mention the time in GMT not morning or evening, because most of the users here are looking for US and canada traffic,
Interesting I never really considered that, wouldn't evenings be better since more people are on to push your digg to the front page?
I always thought it would be better in the evenings but I don't know. If it's a news story then I think mornings would be better, before people go to read the newspapers but I don't know.
according to SEOmoz they have the best results on getting their viral articles on the front page if they submit 4pm-6pm and 8:30am-10:30am