With the forthcoming releases for Firefox 44 and new versions of Chromium and Webkit, the use of event.timeStamp will yield a different value compared to what it did before. Therefore for this reason, all versions of ngAnimate will make use of Date.now() to leverage timing values within animations.

Original bug report:
https://bugzilla.mozilla.org/show_bug.cgi?id=1231619#c3

Changes to Chromium:
https://code.google.com/p/chromium/issues/detail?id=160524