How much of my code will likely be affected by Y2038?

Of course, the answer is highly dependent on the code in question. Software that uses time extensively will obviously require more changes than software that doesn’t use time as much. As a rough guideline, it has been estimated that ~6% of all source code needed to be reviewed for Y2K issues. The percent of source code that needs to be reviewed for Y2038 should be around the same.  But also realize that Y2038 may impact stored data in databases, file systems, network protocols, etc., so the issues may extend well beyond just the code itself.