Refers to the period around the end of the previous calendar year, often used in business or personal contexts to talk about events, deadlines, or situations that occurred at that time.
I moved at the end of last year.
The financial results at the end of last year were tough.
Compound of 去年 (kyonen, 'last year') and 末 (matsu, 'end'). The reading is a straightforward combination of the two components.