Average hours per day (American Time Use Survey) This term refers to the average number of hours spent in a 24-hour day (between 4 a.m. on the diary day and 4 a.m. on the interview day) doing a specified activity.
Usually a cats first season is somewhere between 4 and 10 months old with average age around six months. Siamese and Burmese cats are quite precocious and will often have their first season at 4 months of age.
I have had 2 female cats from kittens, and from my experience, they usually come into heat anywhere from 6-8 months. Usually in late winter, early spring is the first time. From that time, they can go into heat every couple of months. My outdoor female once had 3 litters in one year.