If it is above freezing, peel the forms 24 hours after the pour, remove them the next day following. If it is below freezing, leave them in place for a few days with insulated tarps and heat as required based on weather conditions. The wall should not be without supplemental heat for a week.
http://www.diychatroom.com/f19/how-long-cure-concrete-footing-64160/
Most concrete achieves 40-50% of its strength (1500 PSI if its 3000 mix and 2000 for a 4000 mix) within 48 hours. The reason most concrete guys like to pull forms the following day is so they can move onto the next job with their forms and the concrete will continue to strengthen.
http://www.diychatroom.com/f19/how-long-cure-concrete-footing-64160/
Most concrete these days doesnt need 28 days to come to full strength and most achieve it in 14 or so days. That being said people pour walls and within days are already building on it. The reason for this is because framing a house takes time and the full weight of a house wont bare on it for most of the time a month.
http://www.diychatroom.com/f19/how-long-cure-concrete-footing-64160/
If you figure 150 pounds per cubic foot of concrete, you'll only have a little over a pound of weight per square inch for each 1 foot of height (150# divided by 144 sq inches). A ten foot high wall will only put 11 pounds of weight per square inch.
http://ths.gardenweb.com/discussions/2256276/how-long-should-foundation-concrete-cure
Since the actual strength of the concrete in a residential footing is not particularly critical, testing is not required so the 28 day mark has no practical relevance in the field. In fact, if the concrete hasn't reached the minimum strength required by code in 7 days, it's unlikely to get there.
http://ths.gardenweb.com/discussions/2256276/how-long-should-foundation-concrete-cure
In order to understand the function, some terms need defined: Concrete spread footing under a single column: this footing typically has the column in the middle of the footing. As the force acts downward from the column, the spread footing distributes that force to the soil.
http://www.constructionknowledge.net/concrete/concrete_footings.php
How do I Place Concrete Footings? 4. Tricks of the Trade and Rules of Thumb for Concrete Footings: Concrete footings exist to transfer the structural loads from the building (snow load, live load, dead load, wind load, earthquake load, etc.) to the Earth. Obviously, the foundations on a building are critical from a structural standpoint.
http://www.constructionknowledge.net/concrete/concrete_footings.php
1 Concrete wall footing: this footing has continuous wall above. The forces acting downward through the wall are distributed by the wall footing to the Earth.  Concrete spread footing under multiple columns: depending on the column locations and loads, the layout of this footing can vary greatly.
http://www.constructionknowledge.net/concrete/concrete_footings.php
Bonding is better when the footers concrete is green when the walls are formed and poured. The contact between the footers and walls will adhere better when the walls are poured after a few days. There's really no advantage in waiting 28 days for the footers to cure. The curing process with concrete goes on for years to the point where, when fully cured, it starts on the road to breaking down.
http://ths.gardenweb.com/discussions/2256276/how-long-should-foundation-concrete-cure
The footing should cure 2 to 3 days before the wall is placed on it depending on the weather unless you are building a multi-story apartment building or there are unusual gaps and/or steps in the footing or spread footings for point loads or the building is constructed of load bearing prefabricated walls.
http://ths.gardenweb.com/discussions/2256276/how-long-should-foundation-concrete-cure
how long does it take for concrete to set for footers
It take 28 days for concrete to set for footers. It takes 28 days for concrete to set for the footers.