Do I have to apply sunscreen even on cloudy days or days when I stay indoors?

Hello! I’m usually very interested in skincare, and reading your post sparked a question, so I’m leaving this post to ask. We typically make it a must to apply sunscreen when going out on sunny days. However, I am wondering if it is also necessary to apply sunscreen on days when it is cloudy and raining all day, like during the rainy season, or on weekends when we stay indoors without going out at all.

I have heard that UV rays penetrate the clouds even on cloudy days, but I hesitated to apply sunscreen until I was at home because I dislike the stuffy feeling on my skin. Does sunlight coming through the window while indoors also affect skin aging? Or I am curious if indoor lighting can also cause skin tanning.

I would appreciate answers from those who are knowledgeable about skin regarding whether it is okay to skip sunscreen in times like this, or if I absolutely must apply at least a lightweight product for indoor use!