The only requirement is to observe the verity of the hour.
That is, morning prayer fairly early in the morning, mid-day can be said mid-morning, mid-day or mid-afternoon, Vespers in the early evening, and Compline before bed. The Office of Readings can be said at any time but typically in religious communities it is said either the previous evening by anticipation, or very early in the morning (before Morning Prayer), or sometimes even combined with Morning Prayer (theoretically it can also be combined with Vespers or Compline or any other hour; there are rubrics in the General Instructions for that).
So saying Lauds at 6 am or 8 am is fine; whatever fits your schedule. Vespers at 4, 5, 6 or 7 pm is fine. At the abbey I’m attached to,
Vigils 5 am
Lauds 7:30 am
Terce 9:45 am
Sext and None noon
Vespers 5 pm
Compline 7:45 pm.
At Sant’ Anselmo, in Rome, from where I’m writing these words at this moment:
Lauds + Mass (there are rubrics for that combination), 6:20 am
Mid-day prayer 12:50 pm
Vespers 7:15 pm
Compline 8:30 pm
Office of Readings: on your own in private. Sant’ Anselmo is a college so they use the LOTH instead of a monastic breviary.
So you can see there is considerable variation. It isn’t rigid, but individual communities do generally have fixed schedules, otherwise praying in community would be impossible.