How Long Does it Take to Build a Modern Web Framework?

Dear Java web framework authors,

I hope you're doing well and continue to enjoy working on the web framework you created years ago. I'm curious to know something:

 How long would it take you to build your web framework from scratch?

If all the code from your framework magically disappeared tomorrow and you had to write it from the ground up — how long would it take? What if you had a group of 3-5 developers (of your choosing) to help you do it? 

Furthermore, would you write the whole thing line-by-line, or could you borrow code from other open source projects to streamline the process?

Thanks in advance for your response,

Matt