Explain to the lawyer that these things are hand managed and that dates will slip in which have been copied from other headers in other files, making the years

Explain to the lawyer that these things are hand managed and that dates will slip in which have been copied from other headers in other files, making the years in the headers unreliable, and that if it ever came up in court that you'd have to testify to their unreliability -- while also explaining that git was considerably more reliable and that any one individual commit which had incorrect dates could generally be identified by surrounding dates. That will generally tickle their aversion to putting data that could fail under cross examination in front of a court and they'll be more likely to let you delete all the dates entirely. There's literally no reason for them anyway. You don't even need a copyright statement, but you probably do have a copyright file with years in it, and you've got git for supplimentary info on exactly when any given line of code went into the codebase. Also if you're updating every file every year you're losing the information on when a piece of code when into the codebase, which is the only important thing anyway in the case of patent lawsuits, expiration of copyright really isn't an issue worth worrying about (and I think bumping the copyrights every year is wrong policy there as well). While you're at it, remove all the Author lines as well with the people who no longer have anything to do with the project and their old e-mails which don't work.