HTC One M8 for Windows - Manual (Page 139)

Productivity
What you can do in Calendar
Never miss an important date again. You can sync your existing calendars
from your email accounts to your phone and see them in the Calendar app.
You can also add new appointments, create your to-do list, and respond to
invitations that people send you.
§ After you've set up your email accounts, the calendars associated
with your accounts will be synced to your phone.
If you haven't set up your email accounts, see
Email on page 114 to
find out how to add them to your phone.
When you create new appointments on your phone, they will be
synced to the calendars in your accounts.
§ If you've set up a Facebook account, you'll see your Facebook
events in the Calendar app. You can only view and not create or
edit Facebook events on your phone.
Creating a calendar appointment
When creating a new appointment, you can choose which account's
calendar to add it to.
1. On the Start screen, tap the Calendar tile.
2. Tap .
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