Dawnless Day

The Dawnless Day refers to 10 March, T.A. 3019, when fumes from Mordor veiled the Sun in an attempt by Sauron to discourage or misguide his enemies. The veil of Darkness blacked out most of Gondor and Rohan, though some beams of light could pass through it.
Along with the Darkness, a host from Minas Morgul set forth toward Minas Tirith, as witnessed by Frodo, Sam and Gollum who passed the Cross-roads. Later Orcs from the Morannon took Cair Andros and passed into Anórien.
The Darkness was also observed by the Rohirrim who were mustering their Riders and rode from Harrowdale.
On this day Faramir was rescued by Gandalf and Imrahil outside the Great Gate of Minas Tirith and Aragorn II led the Dead Men and the Grey Company, across the river Ringló.
The Darkness was eventually driven away by a south-west wind on the morning of March 15, when Aragorn and his companions came to the Battle of the Pelennor Fields.