I don't want to start a long post rehashing what has been already said, but there's something I want to tell about programming schedules : everyone is so bad at them that there are many jokes about it, like these:

Hofstader's law : "it always take longer than you expect, even when taking into account Hofstader's law"

the Cargill's law: "The first 90% of the code accounts for the first 90% of the development time. The remaining 10% of the code accounts for the other 90% of the development time."

And this hilarious Douglas Adams' quote : "I love deadlines, I love the whooshing noise they make as they go by."

Then I'll conclude with this anonymous word of wisdom: "Confidence, n.: The feeling you have before you understand the situation."