Related Clues:

• See 55-Across
• Calendar page
• Period of time
• Billing cycle, often
• Time period
• Billing period
• Rental period
• Calendar unit
• Its days are numbered
• Third of a quarter
• One of a dozen
• Billing cycle
• It'll last for weeks
• Wall-calendar page
• The 4 in 4/6, e.g.