“旬“ is usually used to describe time and age. The most used circumstances are as following
1. 八旬 in one’s eighties. (or 六旬,七旬,…)
2. 上旬:the first ten-day period of a month
3. 中旬:the middle ten days of a month; mid-month
4. 下旬:the last ten-day period of a month