I have resolved my issue. I ran the following PowerShell queries (found here http://techtrainingnotes.blogspot.com/2012/10/sharepointfinding-column-display-and.html):
$web = Get-SPWeb SiteUrl
$list = $web.Lists["Announcements"]
$list.fields | select Title, InternalName, Hidden, CanBeDeleted | sort title | ft -AutoSize
The internal names of the Start Time and End Time fields are EventDate and EndDate, respectively.