Lord Of The Rings Online: LOTRO Downtime: Monday, August 20 7:00AM - 2:00PM EDT (-4 GMT)

This in from the launcher and the official forums:

The LOTRO game servers will be down on Monday, August 20th from 7:00AM - 2:00PM EDT (-4 GMT) to update the game to Book 10: The City of the Kings! Roheryn will remain open during the downtime. Full patch notes will be available later today!