This is the 3887th most frequent Chinese word.
上个月
Last month.
Here, '上个月' serves as a time expression indicating the previous month when the event occurred.
上个月我去了北京参加会议。
Last month, I went to Beijing to attend a conference.
In this sentence, '上个月' is used to refer to the timeframe of the preceding month for comparison purposes.
上个月的天气比现在更冷一些。
The weather last month was colder than it is now.
'上个月' is employed here to specify the timing of the action of meeting occurring in the previous month.