Moment.js is a library that helps developing with dates. It supports manipulation of dates, parsing or validate dates, for example based on user inputs, and display dates in certain formats. The localization allows you to display or parse user friendly dates based on a locale and will also translated months etc. Moment.js can also handle durations, queries (like checking if a date is before another date) or custom extensions.
Moment Timezone is a extension of Moment.js which supports to work with different timezones on dates. It can show a specific time in different timezones.