Those URLs didn't work as well as I had hoped because they go to the embedded calendars. Here's a better option: all of the calendars can be imported into your google calendar account at once with the link below. (However, they don't get combined, so you can still turn them on and off individually, and they do not add anything directly to your personal calendar, so you can choose individual events to add.)2018 CodeMash google calendars
As a bonus, you can use the search functionality of Google calendar to find events. To do this, sign into your google account, load all of the calendars using the link above, and then turn off any calendars you don't want to search. Then use the search bar at the top to look for a topic, speaker, or location. The events include the abstracts in the calendar event description, so you can search those too. (Obviously, you should look at January 2018 or else you won't see much on the calendars because the events haven't occurred yet.)
The mobile version of Google calendar works pretty well, in that it will cache events for offline viewing, and it can still do some searching without wifi.