What does ~ = do in javascript

Question

I can't seem to understand what "~ =" does in JavaScript. I watched this tutorial and I saw it. I could not understand what this symbol is called, so if they are already asking for it, tell me and I will delete this post, thanks in advance. Specific line:

window.requestAnimationFrame(function(/* time */ time){ 
  // time ~= +new Date // the unix time 
});