iron-time-behavior 
Polymer hybrid behavior that provides time-from-now string, e.g. today, yesterday, this week, earlier.
The element builds on the momentjs library.
To use this element:
bower install iron-time-behavior
iron-time-behavior uses Moment.js, and so supports all locales that Moment.js supports. But,
the component does not reference any specific locale, so when you want to use it with a locale other than en you must
load the locales explicitly.
<link rel="import" href="bower_components/iron-time-behavior/iron-time-behavior.html">
<script src="bower_components/moment/min/locales.js"></script>
This software is licensed under the Apache 2 license, quoted below.
Copyright 2011-2015 Collaborne B.V. <http://github.com/Collaborne/>
Licensed under the Apache License, Version 2.0 (the "License"); you may not
use this file except in compliance with the License. You may obtain a copy of
the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
License for the specific language governing permissions and limitations under
the License.