Add a Subscribed Calendar to your iPhone
First, copy the calendar link from the TTUIM page. Then go into your Settings and select "Passwords & Accounts".
Then select "Add Account" and chose "other." Chose "Add Subscribed Calendar" and paste the link into the Server field. Select "Next", then "save." All done!
The Conference Calendar should be added to your iPhone now. This calendar will update with changes automatically. Enjoy!