I don't recall anything in the written record about the bedtime rising of the pre-contact Chamorros. Of course, there's a lot to go through so maybe there is mention of it somewhere.
But what is easily called to mind is the description, by missionaries and others, that the Spanish-era Chamorros were early risers and were proud of it. How early? Try 4AM!
Even today, from Guam to Saipan, if you go to a 6AM Mass in church, you're likely to see many man åmko'. I know of senior volunteers who opened churches at 5AM or earlier - in the recent past, not ages ago.
Reasons for such a habit?
Farming on Guam
Nobody wants to be out in the fields past 10 or 11AM in the boiling sun. Spanish-era Chamorros did much more farming than their ancestors, who did more gathering and fishing. So our forebears tried to get as much of the outdoor work over with before midday. Tilling the soil as soon as the sun rose (6AM or so) meant being up by 5, if not earlier. During the hot part of the day, one ate, took a siesta, worked in the shade. Then, one could resume more outdoor work when the sun was less brutal towards the end of the day.
The routine of the day was regulated by the church bell. At the first bell (åtba) got people up, to get started preparing for Mass. That bell was rung at 4AM, something which the first American governor did not appreciate.