<iframe src="/gcalendar-wrapper.php?src=[google calendar embed url here]" style="border: 0" width="100%" height="600" frameborder="0" scrolling="no"></iframe>
Go to https://calendar.google.com/calendar and get the embed code
Hover to your calendar and click the arrow down symbol. Then click Calendar Settings.
You can find the embed code in Calendar Details
Download the file here https://github.com/tolabl/tsuchiya_HP/blob/master/gcalendar-wrapper.php