=== Inspiration ===A major inspiration of the hymn seems to have come from the Vulgate translation of Zephaniah 1:15–16:: "Dies iræ, dies illa, dies tribulationis et angustiæ, dies calamitatis et miseriæ, dies tenebrarum et caliginis, dies nebulæ et turbinis, dies tubæ et clangoris super civitates munitas et super angulos excelsos.
: "Dies iræ, dies illa, dies tribulationis et angustiæ, dies calamitatis et miseriæ, dies tenebrarum et caliginis, dies nebulæ et turbinis, dies tubæ et clangoris super civitates munitas et super angulos excelsos.