Why would a lot of code need to be "fixed" just because someone anally retentive wants deterministic builds? If they truly care they can LD_PRELOAD fake date/time libs.
The reason for deterministic builds is to allow those of us who want to use binaries from our distros for convenience sake verify that the binary is actually built from the source it claims to be from. It only takes a few people actually doing it to confirm things are good for all of us.
Basically it lets the lazy masses gain the same level of confidence in what they're running as those who compile everything from source.
I thought this problem was solved a long time ago by the bitcoin developers w/ gitian.
Bitcoin solved it as far as they needed for their own purposes, this project aims to solve it sufficiently to be generally applicable across the entire Debian operating system. The goal is that the entire Debian binary package repository could be audited by anyone who cares to do it. Obviously if it's generic enough to cover all of Debian the same techniques should be usable pretty much across the entire computing world.