On Firefox (I’m running Fx57, dev edition), the “time” field isn’t wide enough to have the hour, minute, and am/pm selector visible at once – and you can only navigate back to the hour field from the am/pm field using shifttab.
There’s also a slight misalignment between the date field and the time field – the time field is a couple of pixels lower than the date field.
Can you reproduce this in Firefox stable? We don’t generally fix bugs from beta/dev versions of browsers as things tend to change multiple times before going stable,
Nope – because <input type="time"> is only available from Fx 57. 
The MDN docs for <input type="time"> note the differences between the implementations on the desktop browsers: specifically, Chrome and Edge use a 24 hour entry, whereas Firefox uses as 12 hour entry + AM/PM field.
As this is new in Fx 57, it’d be good to be ahead of this change. 
The design specs for this feature show that while there will eventually be fancy popup panels added for selection of times, the styling of the <input> itself won’t change.
No repro in FF Quantum 59, stable branch on Windows.
