og_date = "2012-10-01";
console.log(og_date); // => "2012-10-01"
console.log(og_date.split('-')); // => [ '2012', '10', '01' ]
og_date.value would only work if the date were stored as a property on the og_date object.
Such as: var og_date = {}; og_date.value="2012-10-01";
In that case, your original console.log would work.