You can have an offline copy of your Calendar by creating a PDF Version of your Calendar via your Calendar's “Print” dialog. You can access the “Print” dialog by clicking on the gray “Print” button that is located in the upper right-hand corner of your Calendar.
Once the “Print” dialog is open, just set up a print version of your Calendar to your choice of preferences, and check the “Save as File” box in the the print dialog. You can also choose to name your file in the accompanying text field.
Then just click the ”OK" button at the bottom the dialog and a PDF version of your Calendar will automatically download to your computer. You can then keep this file on hand, or email this file to anyone.