If you want to embed a Google Calendar, it can be made responsive by adding the following to the custom CSS of JUST the page in question:
.responsiveCal {
position: relative; padding-bottom: 75%; height: 0; overflow: hidden;
}
.responsiveCal iframe {
position: absolute; top:0; left: 0; width: 100%; height: 100%;
}
And then wrap the IFRAME code in the responsive div.
div class="responsiveCal"
You can also try the Simple Calendar plugin or use The Events Calendar plugin already on the Network