google docs spreadsheet - date count down - then email

Say we use today Feb 11,2014 and there is a hard coded date in the future Feb 11, 2015 so 365 days left. I'd like google spreadsheet to email when the counter goes to 30 days left. I thought google spreadsheet is better since I don't want to be in the file all the time. col1 col2 remaining Feb 11,2014 Feb 11, 2015 365 then this 365 hits 30 days i'd like an automatic email sent. Like a condition.