The phrase “糊窗户” refers to the practice of pasting paper cutouts (similar to the one seen here) on one's windows. There's a common larger saying, “二十五，糊窗户”, which I assume means that this is usually done on the 25th day of the lunar month. (I'm not sure which one.)
What is the meaning and significance of this phrase? What does it refer to? When is it used?