Advance Purchase: Save 15% Off Booking At Millennium Hotel, U.S. Book 14 days in advance and save 15% off best flexible rate at Millennium hotels across the U.S. T&C: Valid for booking and stay: Now until 31st March 2016. Offer is subject to availability at participating U.S. hotels. Advance purchase of 14 days required with one night prepayment at time of booking. Savings quoted is based on the Best Flexible Rate at point of booking and may vary by hotel. Book Now.