When you have an active fast, you'll see:
On the Daily Log:
A running timer showing how long you've been fasting
The time your fast started
The time your fast will end
A Stop Fast button
At the top of any day's view:
A "Fasting active" indicator
When less than 30 minutes remain, you'll see "Fasting ends in X min"
The fasting card only appears on today's Daily Log, but the active fast indicator shows on any day you're viewing.