One of the main benefits of Google Calendar is the ability to be able to share your calendars with colleagues. Once you have set your calendar as shared, the people you have shared it with will be able to open it in their browser, along with their own calendar, to see your availability at any time.
To allow everyone at your organisation to access your calendar:
Under My Calendars, position the mouse over the calendar you wish to share, then click on the ellipses that appear
Choose Settings and sharing
To share your calendar with everyone in your organisation, check the Make available for (your domain) box
Choose how you want your calendar to be viewed within your organisation, showing only when you are free or busy without any appointment details, or showing all event details
Click on the Back button to return to the calendar