Google Calendar - Spend less time managing your day & more time enjoying it
Freshservice - Freshservice: the one-stop cloud solution for all your IT management needs.
Business Calendar - Powerful and easy to use calendar app for Android including weather, widgets and tasks.
Freshdesk - Freshdesk is a cloud-based customer support software that lets you support customers through traditional channels like phone and email, social channels like Facebook and Twitter, and your own branded community
Jorte - Schedule books must be practical and has a good design.
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.