I get tired of these new studies. I have done calendar for 5 years. My kids do very well with it. My children can count, know the days of the week and the months in order. We also count the days we have been in school. My children can count by 10s by the end of the year. I also heard that we are to quit letter of the week. I am still concentrating on a letter a week but my units no longer correlate with it. I also review all letters I have been doing. I don't think you should quit calendar unless you feel like you want to.