I have chosen to just remove years from copyrights/licenses.<p>AFAIK the copyright isn't invalidated by not giving a date; In fact I'm not even sure if a copyright notice is required at all.<p>Copyright years seem to be understood differently anyway. I've heard that it should be the <i>beginning</i> of the copyright, so there is no need to change it. The problem is that your copyrighted work is probably changing, so that brings up the question if those changes would justify a change to the date or not. I have also seen the format of "2013, 2015" or "2013 - 2015" using the first version's year and the current year.<p>It's all a big mess IMO