The Rule of St. Benedict

Making due allowance for circumstances, the brethren will rise during the winter season, that is, from the calends of November till Easter, at the eighth hour of the night; so that, having rested till a little after midnight, they may rise refreshed. The time, however, which remains over after the night office (Matins) will be employed in study by those of the brethren who still have some parts of the psalms and the lessons to learn.

But from Easter to the aforesaid calends, let the hour for celebrating the night office (Matins) be so arranged, that after a very short interval, during which the brethren may go out for the necessities of nature, the morning office (Lauds), which is to be said at the break of day, may follow presently.