When do lines open up on betting sites?

Relatively new to betting ATS and money lines via the Internet sites and just wanted to exactly when they release the lines...i use bovada and I notice Tuesday I can get most lines here on Covers but bovada doesn't open any NCAA till usually I check Wednesday early EST. I didn't know if it was a set time they are able to do so or if it's a random thing, I know obviously certain games open/close due to player info/money thought out the week

Thanks

If my book here in Australia doesn't have market up I usually call the customer service and they get it up straight away.

most will have them listed once both teams have completed their previous games. 

sbr forum has opening lines listed for each sport under odds.

sunday evening around 4 pm you can find college lines up at several casinos, around 630 pm you can see the pros popping up. eastern time zone. cris, eagle, carib, betonline,greek.grande.

checkout donbest.com  when they post their opening lines you will see other casinos have them up as well.    if there is no line typically you won't find many casinos posting anything either.