Convert a Firebase Push ID into Unix time (https://gist.github.com/mikelehen/3596a30bd69384624c11/)

getPushIdTimestamp.js

var getPushIdTimestamp = (function getPushIdTimestamp() {
  var PUSH_CHARS = '-0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz';

  return function getTimestampFromId(id) {
    var time = 0;
    var data = id.substr(0, 8);

    for (var i = 0; i < 8; i++) {
      time = time * 64 + PUSH_CHARS.indexOf(data[i]);
    }

    return time;
  }
})();

Java port:

private final static String PUSH_CHARS = "-0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz";
public static long getTimestampFromId(String id) {
    long time = 0;

    String data = id.substring(0, 8);

    for (int i = 0; i < 8; i++) {
        time = time * 64 + PUSH_CHARS.indexOf(data.charAt(i));
    }

    return time;
}

Python 2.X/3.X port:

def keyToTimeStamp(key):
        PUSH_CHARS ='-0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz'
        idString = key[0:8]
        time = 0
        for letter in idString:
                time = time * 64 + PUSH_CHARS.index(letter)

        return time