Timezone.io - Keep track where and when your team is.
Slack - A messaging app for teams who see through the Earth!
Time Zone Pro - A beautiful world clock for friends, family, clients and more
9mCollab - Collaborate (efficiently) Conclude (fast) Contribute (in the knowledge base)
Spacetime - Work hour and time zone management for distributed teams.
Mattermost - Mattermost is an open source alternative to Slack.