My female dog acts strange and bled for only one day during her period—is this normal?

Bleeding for only one day is not normal; dogs usually start estrus and menstruation at 8 months, twice a year, with bleeding lasting 7-14 days, though timing and amount vary by individual and size. Still, when bleeding lasts just one day, take the dog to a vet to rule out reproductive-system disease. During estrus, under sex hormones, most dogs change in temperament, mood, and appetite, crave going out to mate, and become unstable; if taking a female in heat outside, put sanitary pants on her to avoid being chased or mounted by males and an accidental pregnancy.