If You don't have google account sign up one.
If You have google account (gmail or whatever google service so you
can login) go to calendar.
If you need to set up a new calendar, then do it, it's super simple.

Then go to schedule http://www.hyperisland.se/schedule/
choose calendar you are interested in and click on the +googlecalendar
button which is at the bottom-right corner of the calendar page.

You can see now that schedule was added to your calendar on the left
side of the web page under „other calendars” tab.
Now click on settings (red circle on the picture).

1. Click on „mobile setup” tab.
2. Choose Your country (most probably Sweden)
3. Put Your phone number (Your mobile operator is most probably supported)
4. Wait for verification code – it will be texted to your cellphone – and type it.

Click on „Calendars” tab.
Then click on „Notifications” next to schedule as shown in the picture.

Click on add a reminder

Now choose SMS from dropdown list and set the delay of time You would like to
be notified before each event.
Save changes. And You're done. You don't need to ever visit your google calendar
or schedule again. You can play with adding more calendars and separate
notifications on Your own. Whatever.