According to various traditions, the outcome of a spell may take as little as a day or two or as long as several weeks. In many Pagan traditions, the general rule of thumb is that if you haven't seen something begin to manifest within four weeks (one lunar cycle), then you may need to revisit your work.
 
How Do You Know if a Spell Is Working? 
Typically, spells don't result in immediately visible outcomes. For example, a love spell may start with changes in the feelings of the person on whom the spell is cast. Even after their feelings have changed, it may take time for feelings to turn into actions or to develop fully.