Press the "CAL A1 / A2" button on the top right to cycle through the alarms until the calendar (month and day) is displayed on the bottom left. You can't set the clock if one of the alarms is showing.
Now hold down the "CAL A1 / A2" button for about two seconds until "12 Hr" begins to flash.
Go through each time setting by pressing the "CAL A1 / A2" button, and use the top and middle buttons on the right-hand side to change the value up and down.
This allows you to change:
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