I was reading a conversation and came to these sentences :
爸爸 :双十一是什么?
妈妈 :就是11月11号的网上购物节,在网上买东西很便宜。
I was wondering why it's 号 instead of 日. I then checked it on the dictionary and found out that 号 can mean "the day of the month".
I have looked for an answer but not sure whether or not what I found is correct. It's said that 日 is more formal than 号 and that 号 is used when you speak casually. Is that true? And is there any more difference between both words?
Thank you.