According to Sakurai he will be updating the official Smash Bros site every weekday during his lunch break. When he was updating the Dojo back in 2007, he was very consistent with the time that he did this. For most of the updates, he did them between 12PM and 3PM Japan Time. In order to help you guys figure out what time it will be when he updates in your respective state/country, here’s a helpful Time Table.
“Japan Time”(12PM-3PM Monday through Friday)
United States West Coast- (8PM-11PM Sunday through Thursday)
United States Mountain, Western Canada- (9PM-12AM Sunday/Monday through Thursday/Friday)
United States Midwest, Mexico, Central Canada, Central America- (10PM-1AM Sunday/Monday through Thursday/Friday)
United States East Coast, Eastern Canada, Caribbean Islands, Brazil, Argentina- (11PM-2AM Sunday/Monday through Thursday/Friday)
United Kingdom, Ireland, Portugal, Morocco- (4AM-7AM Monday through Friday)
Spain, Germany, France, Austria, Netherlands, Poland, Italy, Hungary, Sweden, Switzerland, South Africa- (5AM-8AM Monday through Friday)
Greece, Israel, Jordan, Saudi Arabia, Turkey- (6AM- 9AM Monday through Friday)
Russia- (7AM-10AM Monday through Friday)
Pakistan- (8AM-11AM Monday through Friday)
India, Sri Lanka, Nepal (9AM-12PM Monday through Friday)
China, Hong Kong (11AM-2PM Monday through Friday)
Australia West Coast(12PM-3PM Monday through Friday)
Australia East Coast (1PM-4PM Monday through Friday)
New Zealand (3PM-6PM Monday through Friday)
Obviously this does not list every country in the world but you should have a general idea of when you'll see them based on this. Also keep in mind that there will be some nights/mornings where the updates will be significantly later for whatever reason so this time table is not absolute every update night.