Possible Clues:

• Hour to be home by
• Early indoors imposed by military
• Requirement to be indoors at a set hour
• Lately it sounds for a single beast and not many more
• Early bed-time imposed by military
• Early closing time imposed by military
• Regulation restricting movement at night
• Restriction on night-time movements
• Nighttime limitation on movement
• Restriction on nocturnal movement