[gumby]

> Interestingly, the date line wasn't always where it is now.

Different empires defined their own prime meridians (and thus implicitly their date line 180 degrees away) from the ~16th-19th century. Eventually in the late 1800s a conference was organized to pick one and since Britain was the center of commercial shipping (with all the concomitant infrastructure like Lloyds, project finance, Admiralty law etc) there was little dissent.