Embed Multiple Calendars - classic Google Sites
Google has released several new features, two of which allow for easy embedding so you can now embed multiple Google Calendars that appear all in one.
Go to your Google Calendar and go to its settings - see screen shot
Google Calendar Settings Menu.
Use the Customise the colour, size and other options link in the Embed Calendar section to choose which calendars you want to display - see screen shot
Google Calendar Embed Calendar
Choose the various settings you want and the calendars you want to display and copy the HTML code from the box (use the keyboard shortcut to copy [Ctrl+C in Windows and Linux and cmd+C on a Mac] as using the context [right-click] menu does not work).
Go to your Google Site, use the Edit Page button on the page you want the calendar on, then use the Insert button, then choose More Gadgets.
From the list of categories on the the left choose Featured and then choose Embed Gadget (you may need to scroll to find it) and use the Add button.
Paste the code you copied into the Embedding snippet box (use the keyboard shortcut to copy [Ctrl+V in Windows and Linux and cmd+V on a Mac] as using the context [right-click] menu does not work) and make sure you enter the width and height the same as you set in the Embed Calendar tool, then use the Add button, then the Save button and view the inserted Google Calendar.
See the video how to below for more detailed instructions