Plan · Bucketlist Tours
The Viewing Calendar
Every night of the year at La Parguera, rated on how long the bay is truly dark.
The calendar needs JavaScript to calculate each night.
Select a night to see its sunset, darkness, moonrise and moonset.
- Dark the whole time
- Late moonrise: a night nobody counts
- Dark for part of it
- Moon up: a bright night
This calendar predicts darkness, not brightness. Poor nights are marked as poor. Ratings assume we are in the water for the 90 minutes after full darkness arrives.
Calculated for La Parguera, Lajas, Puerto Rico. Carlos A. López Ruiz, Bucketlist Tours. You are welcome to cite this calendar with a link to this page.
Most calendars for the bioluminescent bays are moon phase charts. A phase chart tells you how much of the moon is lit. It does not tell you whether the moon is in the sky while you are in the water, and that is the only question that matters.
This calendar answers that question for every night of the next twelve months.
What it calculates
For each date, at the coordinates of the bay itself and not San Juan, it works out:
- the time the sun sets
- the time real darkness arrives, which is later than sunset
- the time the moon rises and the time it sets
- how much of the moon is lit
- and from those, how many minutes of true darkness fall inside the hours we are on the bay, with no moon above the horizon.
How to read it
Each night is rated on its dark minutes, not on the phase.
- Dark the whole time. The moon is down for the entire window.
- Dark for part of it. The moon rises or sets while we are out.
- Moon up. A bright night. Read the note about the pontoon below.
- Late moonrise. Marked on its own. These are the nights nobody counts: the moon has not come up yet when darkness falls, and it does not rise until after we are finished. There are eight to ten of them in most months.
Open any date to see its sunset, the hour of darkness, moonrise, moonset and illumination.
The window this calendar assumes
The ratings are built around arriving at the bay after sunset, not around the hour we leave San Juan. The window used is. If your tour with another operator runs at a different hour, the rating for your night may be different.
Why the same moon gives a different night in June and December
In winter the sun goes down around 6:30 and the bay is fully dark by 7:00. In summer it can be close to 8:00 before there is real darkness. A moon that rises at 8:30 gives you an hour and a half of true dark in December and barely forty-five minutes in June.
Same moon. Same phase. Completely different night.
What this calendar cannot tell you
It predicts darkness. It does not predict brightness.
A peak glow on the fourth of July in 2023 became a fifty percent night on that same date in 2025. The glow depends on the days before: how much sun the bay had, how much it was stirred, whether it rained, whether the Sahara dust was over us. If I was out there yesterday and it was at peak, chances are it will be bright for the next couple of days. Beyond that, nobody can honestly promise.
Poor nights are marked as poor. A calendar that rates every night well is worthless.
If your night is a bright one
Come anyway, but come on a platform that makes its own darkness. We go out on a pontoon even at eighty percent moon, and on those nights we are usually the only boat on the bay. Those are not optimal conditions and I will not tell you they are. But the glow is always evident under the platform.
If you can choose your dates
Choose a dark night between October and early December. The nights are longer, the window is wider, and you will have the bay to yourself.
Why the window moves, and how to read the water
Calculated for La Parguera, Lajas, Puerto Rico. Carlos A. López Ruiz, Bucketlist Tours. You are welcome to cite this calendar with a link to this page.