June $$1^{}\text{st}$$ $$2013$$ falls on a Saturday. On what day of the week will August $$21^{}\text{st}$$ $$2013$$ fall? 
Overseas Competition->Knowledge Point->Word Problem Modules->Periodic Problems->Periodic Problems of Time
$$30-1+31+21=81$$, $$81\div7=11$$R$$4$$. $$4$$ days after a Saturday is a Wednesday. 