Precursor to Dies iræ

I remember singing Hindemith’s setting of this a few years back. Great piece.

Apparebit repentina dies:
http://www.spectrumsingers.org/archives/1995-96/jan96_words.html

No later than 7th century in origin. Hmm - does this mean the people who decry Dies iræ as an over-the-top medieval “accretion” are ignorant of this prayer, which contains many of the same ideas (at least, the “over-the-top” ones)?