Possible Clues:

• Pre-weekend "Phew!"
• Working stiff's sighed line
• "The weekend's almost here!"
• End-of-the-week business letters?
• 'The weekend's here at last!'
• Letters after forty hours
• 'What a long week this was!'
• 'Good riddance to this week!'
• Ready-for-the-weekend cry
• Fri. refrain?