If February contains Friday the $$13^{}\text{th}$$, what day of the week is February $$1$$st?． 
Overseas Competition->Knowledge Point->Word Problem Modules->Periodic Problems->Periodic Problems of Time
We can count backward by days or by weeks. Count a few weeks back to find that February $$6$$ is a Friday. Then count a few days back to find that February $$1$$ is a Sunday. 