a contango day的用法和样例：
- I bought a pair of tan leather shoes the other day.
- Normally, the nearby months are less expensive than the faraway months, and that relationship is called a contango market.
- He has a large amount of mail to answer every day.
- People in this locality used to take two meals a day.
- It's natural to slack2 off towards the end of a hard day's work.