Christmas night brings one of my very favorite rubrics of the whole liturgy:
In eadem nocte Nativitatis, veritas horarum impedit regulariter ne Laudes matutinae statim post Missam de nocte celebrentur.
As Englished by our American Liturgy of the Hours: "The plan of the hours demands that Morning Prayer not be celebrated immediately after the Mass at midnight, but in the morning."
Sorry, efficient pray-er! The temptation is easy to imagine. Having offered or assisted at the Mass in nocte, which replaces Night Prayer, and with the Office of Readings already having been prayed in its rightful place beforehand, one might have the temptation to dive right into Morning Prayer, so as to have more time to rest in the morning! Not so fast, says our rubric; Morning Prayer is for the morning. Veritas horarum.
This has to be said, given that the rubric in the older Breviarium Romanum says the exact opposite! After the collect following the third nocturn of Matins, so says the older rubric:
Et dicto Benedicámus Dómino, celebratur prima Missa post mediam noctem, ut in Missali: qua finita, dicuntur Laudes.
"Having said the Benedicámus Dómino, the first Mass is celebrated after midnight, as in the Missal. After Mass, Lauds is said."