I've set up a macro to replace what Quickeys did for me - open my junk mail folder in Apple Mail. When I use the "Try" button at the bottom it works perfectly. Yet, when I stagger to the computer with my coffee in the morning, the time scheduling part apparently doesn't work. What am I missing here?
Not a stupid question, but maybe a stupid answer now: The macro will only trigger when the computer is not sleeping.
From the Wiki:
Remember that the Mac must be awake for the trigger to happen, and if the Mac is sleeping the macro will not fire at a later time.
Please don’t hesitate to ask questions! KM has so many features, most of us still haven’t learned them all. Chances are, if you have a question, someone else will have the same question.
So go ahead and ask! We won’t ridicule you. 
I inserted “Wake Screen” after the schedule and before activating Mail. As my screen, but not my hard disk sleeps (now), I’m thinking I should wake up tomorrow to my Junk folder open. We’ll see. Thanks.
You have a very valid question, so I changed the Topic Title to reflect the question. This will help others find your topic.
While we encourage everyone to do their own research/homework before posting, there is no such thing as a "stupid question". As others have posted, if you have the question, then very likely others will as well.
Lots of good help available here. I'm sure someone will be able to point in you the right direction.
The screen sleep shouldn’t affect the macro triggering – as long as you have not set your computer to ask for a screensaver password (System Preferences > Security & Privacy).
The disk sleep shouldn’t affect it either.
The important thing is that the computer is awake → Check your settings in System Preferences > Energy Saver. You have to set the “Computer sleep” to “Never”, or set a “Startup or wake” schedule in the same Preferences pane.
There is also a setting in the Energy Saver preferences that might have an effect:
I have no idea if Keyboard Maestro Engine can function under the "Power Nap" setting. @peternlewis?
Good advice. Thanks. Just set my iMac to wake at 3:58 A.M.
A sleeping screen, with an awake computer, will not stop macros from triggering - but it will stop UI actions from working. The system disables most of the UI when the Mac display is sleeping or screen saving or locked.
You really shouldn’t have to get up this early 
Agree. Retired but sub at my old school 30 miles away sometimes. Requires a 4 A.M. wakeup.