There actually isn't any specific time frame. It all depends on the type of seafood, the conditions under which it has been stored before and after sale and the size of the bacterial load.
If you are referring to refrigerated fresh fin fish, use it within 1-2 days of purchase.
See this site from Clemson University Cooperative Extension Service:
http://hgic.clemson.edu/factsheets/HGIC3522.htm
About four to five days, properly refrigerated.
24 hours
Refrigerated breast milk is good for up to 24 hours after warming it up.
Refrigerated breastmilk is good for up to 4 days before it needs to be discarded.
3 days
Refrigerated pasta is typically good for 3-5 days before it goes bad.
A refrigerated boiled egg is typically good for about one week before it should be consumed.
About a week if refrigerated.
Seafood is generally good in the fridge for 1-2 days before it goes bad.
Refrigerated hard boiled eggs are typically good for up to one week before they spoil.
If refrigerated, maybe upwards of a week.
Vegetarian Chili is good for about 4 days after it is cooked. This is only if it is refrigerated of course.