Joel 2: 1 - 2
1 Blow the trumpet in Zion; sound the alarm on my holy mountain! Let all the inhabitants of the land tremble, for the day of the LORD is coming, it is near,
2 a day of darkness and gloom, a day of clouds and thick darkness! Like blackness there is spread upon the mountains a great and powerful people; their like has never been from of old, nor will be again after them through the years of all generations.

EWTN