You need a google account in order to get started with Google Calendar and once you are logged into your google account you need to login to Google Calendar to start creating your events where in you would recieve your alert notifications via SMS. Once you are logged into the Google calendar interface you will be shown a large table like spreadsheet with hour basis options and you need to just click on any tab to enter a notification or event.

Recently there were some issues with Google calendar allowing spammers to create events in calenders and here is one of the screenshot of the same. The Google Calendar team is also working out on these nigerian spams recieved by google calender users.

Here is the procedure to avoid it :

Click on the settings tab on the top of any google calender page and select General tab and in the automatically add invitations to my calender section select ‘No’ and click on save, after which you are done.

This is currently the only best way to avoid spam in Google calenders.