After upgrading to iOS 7, I lost my subscribed calendars. Why?

There appears to be known glitches in iOS 7 with regards to subscribed calendars: http://forums.imore.com/ios-7/262240-subscribed-calendars-gone-ios7-help.html

The issues appears to get fixed after turning off SSL on the subscribed calendars. Let's try these steps:

1. Go to iPhone Settings
2. Go to "Mail, Contacts, Calendars"
3. Drill into the calendars you are missing (one by one)
4. For each calendar, turn "Use SSL" OFF and save.
5. After you finish all of them, go back to iCalendar and ensure the calendars in question are all marked for display.