Lately my mom cannot tell if it's night time or day time, is that normal?

Yes, she was already diagnosed with Alzheimer's but I wasn't sure if this was normal. Thank you JoAnn I was very concerned because last night she got extremely upset when I told her it was night and started crying. My poor mom!!!!

No, this is a sign of Dementia. You need to take her to her doctor. If my Mom took a nap she thought it was the next day when she woke up. Would wake up a night thinking it was time to get up. I kept telling her if it was dark outside it was not time to get up.