Every tour on Mosquito Bay stops for three nights around each full moon, and on the other nights the moon decides how much of the glow you see. This is every night of 2027 at the bay, from the US Naval Observatory’s figures for Mosquito Bay itself: the 36 nights with no tours, and for every other evening, what the moon is doing while the boats are on the water.
All dates and times are Atlantic Standard Time, which Vieques keeps all year. From 14 March to 7 November 2027 that is the same clock as US Eastern Daylight Time; the rest of the year Vieques is an hour ahead of New York.
2027 at a glance
One row per month. No tours are the closed nights. Out of the sky all evening are the runs of nights when the moon is below the horizon from 6:30 to 10 PM, the darkest the bay gets. A run that crosses from one month into the next is listed under both.
| Month | Full moon | No tours | New moon | Out of the sky all evening |
|---|---|---|---|---|
| January | 22 Jan, 8:17 AM | 21–23 Jan | 7 Jan, 4:24 PM | 28 Dec – 7 Jan; 26 Jan – 6 Feb |
| February | 20 Feb, 7:23 PM | 19–21 Feb | 6 Feb, 11:56 AM | 26 Jan – 6 Feb; 24 Feb – 7 Mar |
| March | 22 Mar, 6:44 AM | 21–23 Mar | 8 Mar, 5:29 AM | 24 Feb – 7 Mar; 26 Mar – 6 Apr |
| April | 20 Apr, 6:27 PM | 19–21 Apr | 6 Apr, 7:51 PM | 26 Mar – 6 Apr; 24 Apr – 5 May |
| May | 20 May, 6:59 AM | 19–21 May | 6 May, 6:58 AM | 24 Apr – 5 May; 24 May – 3 Jun |
| June | 18 Jun, 8:44 PM | 17–19 Jun | 4 Jun, 3:40 PM | 24 May – 3 Jun; 23 Jun – 2 Jul |
| July | 18 Jul, 11:45 AM | 17–19 Jul | 3 Jul, 11:02 PM | 23 Jun – 2 Jul; 23 Jul – 1 Aug |
| August | 17 Aug, 3:29 AM | 16–18 Aug | 2 Aug, 6:05 AM; 31 Aug, 1:41 PM | 23 Jul – 1 Aug; 23–30 Aug |
| September | 15 Sep, 7:03 PM | 14–16 Sep | 29 Sep, 10:36 PM | 21–30 Sep |
| October | 15 Oct, 9:47 AM | 14–16 Oct | 29 Oct, 9:36 AM | 20–29 Oct |
| November | 13 Nov, 11:26 PM | 12–14 Nov | 27 Nov, 11:24 PM | 18–28 Nov |
| December | 13 Dec, 12:09 PM | 12–14 Dec | 27 Dec, 4:12 PM | 17–27 Dec |
The dark runs are longest early in the year: 12 nights at a time from late January to early May. They shorten through the late summer to 8 nights at the end of August, and run 10 or 11 nights in the fall.
The three closed nights
Every operator on the bay closes on the same nights. Abe’s Snorkeling & Biobay puts it plainly:
“All biobay tour companies in Vieques are closed during the night before the full moon, the night of the full moon, and the night after the full moon every month per DRNA regulation.”
JAK Water Sports says the same of the DNER’s rules, “the day before, the day of, or the day after the full moon each month”, and Alikei Adventures lists the same three days as closed. DRNA and DNER are the Spanish and English initials of the same agency, Puerto Rico’s Department of Natural and Environmental Resources, which manages the bay. Abe’s gives the agency’s reason: “to give the biobay a ‘rest’ from human interaction each month during a time when the bioluminescence will often be less visible.”
With 12 full moons in 2027, that is 36 closed nights. No month of 2027 has two full moons. August has two new moons, on the 2nd and the 31st, and so two dark runs.
The closure follows the date on Vieques. Two of 2027’s full moons come late in the evening, and in Universal Time they fall on the next day: the full moon at 8:44 PM on 18 June is 19 June in UTC, and the one at 11:26 PM on 13 November is 14 November. A moon calendar kept in UTC, or one set for Europe, moves those two closures a night late. On Vieques they are 17 to 19 June and 12 to 14 November. Abe’s points its guests to timeanddate.com’s lunar calendar for San Juan, which keeps Puerto Rico’s clock and gives the same dates as this page.
Month by month, night by night
Each month’s table starts with the run of nights that is under way on the 1st and ends with the run under way on the last day, so a run that crosses a month end appears in both months, whole.
January 2027
December 2026, and the January holidays, are on Vieques and Culebra over the holidays, which runs the same table from late November.
| January evenings | The moon from 6:30 to 10 PM |
|---|---|
| 28 Dec – 7 Jan | Out of the sky all evening. New moon 7 Jan |
| 8–11 Jan | A thin crescent, 1 to 13 percent lit, setting from 6:50 to 9:21 PM |
| 12–20 Jan | Up all evening |
| 21–23 Jan | No tours. Full moon 22 Jan, 8:17 AM |
| 24–25 Jan | Dark until moonrise at 8:40 and 9:37 PM |
| 26 Jan – 6 Feb | Out of the sky all evening. New moon 6 Feb |
February 2027
February to April is the high season on the islands, and the ferry, the holidays and the winter swells for a trip in those months are on Vieques and Culebra in February, March and April 2027.
| February evenings | The moon from 6:30 to 10 PM |
|---|---|
| 26 Jan – 6 Feb | Out of the sky all evening. New moon 6 Feb |
| 7–10 Feb | A thin crescent, 1 to 15 percent lit, setting from 7:18 to 9:47 PM |
| 11–18 Feb | Up all evening |
| 19–21 Feb | No tours. Full moon 20 Feb, 7:23 PM |
| 22–23 Feb | Dark until moonrise at 8:17 and 9:13 PM |
| 24 Feb – 7 Mar | Out of the sky all evening. New moon 8 Mar |
March 2027
Holy Week runs from Palm Sunday, 21 March, to Easter Sunday, 28 March, and the full moon closes the bay on its first three nights. On 24 and 25 March the evening is dark until the moon rises, and from Good Friday, 26 March, the moon is out of the evening sky through Easter. The ferry, the holidays and the school recess that week are on Vieques and Culebra over Holy Week 2027.
| March evenings | The moon from 6:30 to 10 PM |
|---|---|
| 24 Feb – 7 Mar | Out of the sky all evening. New moon 8 Mar |
| 8–11 Mar | A thin crescent, 0 to 11 percent lit, setting from 6:52 to 9:32 PM |
| 12–20 Mar | Up all evening |
| 21–23 Mar | No tours. Full moon 22 Mar, 6:44 AM |
| 24–25 Mar | Dark until moonrise at 8:50 and 9:47 PM |
| 26 Mar – 6 Apr | Out of the sky all evening. New moon 6 Apr |
April 2027
| April evenings | The moon from 6:30 to 10 PM |
|---|---|
| 26 Mar – 6 Apr | Out of the sky all evening. New moon 6 Apr |
| 7–9 Apr | A thin crescent, 1 to 9 percent lit, setting from 7:24 to 9:25 PM |
| 10–18 Apr | Up all evening |
| 19–21 Apr | No tours. Full moon 20 Apr, 6:27 PM |
| 22–23 Apr | Dark until moonrise at 8:31 and 9:27 PM |
| 24 Apr – 5 May | Out of the sky all evening. New moon 6 May |
May 2027
| May evenings | The moon from 6:30 to 10 PM |
|---|---|
| 24 Apr – 5 May | Out of the sky all evening. New moon 6 May |
| 6–8 May | A thin crescent, 0 to 7 percent lit, setting from 7:12 to 9:22 PM |
| 9–18 May | Up all evening |
| 19–21 May | No tours. Full moon 20 May, 6:59 AM |
| 22–23 May | Dark until moonrise at 9:04 and 9:52 PM |
| 24 May – 3 Jun | Out of the sky all evening. New moon 4 Jun |
June 2027
The sun sets latest in early July, at 7:02 PM on the 1st, and the first tours of the night move later with it. In June and July a crescent that sets early in the evening can be down before your boat is out, so read its time against your tour’s.
| June evenings | The moon from 6:30 to 10 PM |
|---|---|
| 24 May – 3 Jun | Out of the sky all evening. New moon 4 Jun |
| 4–6 Jun | A thin crescent, 0 to 5 percent lit, setting from 7:04 to 9:10 PM |
| 7–16 Jun | Up all evening |
| 17–19 Jun | No tours. Full moon 18 Jun, 8:44 PM |
| 20–22 Jun | Dark until moonrise at 8:33, 9:14 and 9:51 PM |
| 23 Jun – 2 Jul | Out of the sky all evening. New moon 3 Jul |
July 2027
| July evenings | The moon from 6:30 to 10 PM |
|---|---|
| 23 Jun – 2 Jul | Out of the sky all evening. New moon 3 Jul |
| 3–6 Jul | A thin crescent, 0 to 10 percent lit, setting from 6:52 to 9:29 PM |
| 7–16 Jul | Up all evening |
| 17–19 Jul | No tours. Full moon 18 Jul, 11:45 AM |
| 20–22 Jul | Dark until moonrise at 8:27, 9:01 and 9:33 PM |
| 23 Jul – 1 Aug | Out of the sky all evening. New moon 2 Aug |
August 2027
Two new moons, on the 2nd and the 31st, and two dark runs.
| August evenings | The moon from 6:30 to 10 PM |
|---|---|
| 23 Jul – 1 Aug | Out of the sky all evening. New moon 2 Aug |
| 2–5 Aug | A thin crescent, 0 to 15 percent lit, setting from 7:17 to 9:24 PM |
| 6–15 Aug | Up all evening |
| 16–18 Aug | No tours. Full moon 17 Aug, 3:29 AM |
| 19–22 Aug | Dark until moonrise at 8:08, 8:42, 9:18 and 9:57 PM |
| 23–30 Aug | Out of the sky all evening. New moon 31 Aug |
| 31 Aug – 4 Sep | A thin crescent, 0 to 20 percent lit, setting from 6:35 to 9:22 PM |
September 2027
| September evenings | The moon from 6:30 to 10 PM |
|---|---|
| 31 Aug – 4 Sep | A thin crescent, 0 to 20 percent lit, setting from 6:35 to 9:22 PM |
| 5–13 Sep | Up all evening |
| 14–16 Sep | No tours. Full moon 15 Sep, 7:03 PM |
| 17–20 Sep | Dark until moonrise at 7:19, 7:57, 8:40 and 9:27 PM |
| 21–30 Sep | Out of the sky all evening. New moon 29 Sep |
October 2027
| October evenings | The moon from 6:30 to 10 PM |
|---|---|
| 1–4 Oct | A thin crescent, 3 to 24 percent lit, setting from 7:13 to 9:39 PM |
| 5–13 Oct | Up all evening |
| 14–16 Oct | No tours. Full moon 15 Oct, 9:47 AM |
| 17–19 Oct | Dark until moonrise at 7:25, 8:17 and 9:15 PM |
| 20–29 Oct | Out of the sky all evening. New moon 29 Oct |
| 30 Oct – 2 Nov | A thin crescent, 2 to 18 percent lit, setting from 6:36 to 9:16 PM |
November 2027
The full moon is at 11:26 PM on the 13th, so the closed nights are the 12th to the 14th.
| November evenings | The moon from 6:30 to 10 PM |
|---|---|
| 30 Oct – 2 Nov | A thin crescent, 2 to 18 percent lit, setting from 6:36 to 9:16 PM |
| 3–11 Nov | Up all evening |
| 12–14 Nov | No tours. Full moon 13 Nov, 11:26 PM |
| 15–17 Nov | Dark until moonrise at 7:06, 8:09 and 9:13 PM |
| 18–28 Nov | Out of the sky all evening. New moon 27 Nov |
| 29 Nov – 2 Dec | A thin crescent, 3 to 19 percent lit, setting from 7:04 to 9:45 PM |
December 2027
Christmas 2027 falls in a dark run: the moon is out of the evening sky from 17 to 27 December. The year before is the other way round, with the full moon closing the bay from 22 to 24 December 2026.
| December evenings | The moon from 6:30 to 10 PM |
|---|---|
| 29 Nov – 2 Dec | A thin crescent, 3 to 19 percent lit, setting from 7:04 to 9:45 PM |
| 3–11 Dec | Up all evening |
| 12–14 Dec | No tours. Full moon 13 Dec, 12:09 PM |
| 15–16 Dec | Dark until moonrise at 8:05 and 9:09 PM |
| 17–27 Dec | Out of the sky all evening. New moon 27 Dec |
| 28–31 Dec | A thin crescent, 1 to 13 percent lit, setting from 6:45 to 9:17 PM |
Picking a night
The darkest run ends with the new moon. Before it, the waning moon rises after 10 PM and the whole evening is dark. After it, a young crescent hangs low in the west at dusk and sets early: in 2027 it is never more than a quarter lit, and the later tours of those nights are dark.
After the full moon, go early. On the two to four nights after each closure the evening is dark until the moon rises, half an hour to an hour later each night. Alikei Adventures recommends the same thing: “the week after the full moon on the early tour times.” The week before the full moon is the opposite, with the moon high in the sky from sunset.
A moonlit night is not a lost one. Abe’s tells its guests that cloud cover “may help to block the moon and its light”, and that the glow is often bright even on the nights around the full moon. Alikei puts the other side: the glow is still there under a strong moon, but harder to see. If the only night you have is a moonlit one, go on the earliest tour after a full moon or the latest before one, whichever the table puts in the dark.
The moon table on the Mosquito Bay page centers nine nights on each new moon, counted forward from the day the site was last built. Its new moon dates are the same as these. This calendar counts the hours the boats are on the water, which puts the darkest nights a little earlier, ending with the new moon itself.
Which boat
All three trips on this page leave from Vieques itself, so the night you choose is the night you go out. If anyone in the group would rather not paddle, the electric boat is the one: Isla Nena’s 40-minute trip on the bay. For children or first-time paddlers, Adventure Vieques runs its clear canoes for all ages and experience levels, and you watch the glow through the hull. Alikei Adventures runs clear kayaks for everyone else. Why the moon decides the night, and the rules on the water, are on the Mosquito Bay page.
If you are sleeping in San Juan, Mosquito Bay from San Juan in a day works on the first tour of the night and the last ferry back, so pick a night when the early evening is dark.
How the calendar is worked out
Tour planners, forums and other guides are welcome to quote or reprint these dates. A link to this page lets your readers find any correction, which we log on our changes page.
- The figures are the US Naval Observatory’s, from its Astronomical Applications API, read on 12 October 2026: the times of 2027’s new and full moons, given in Universal Time and converted here to Atlantic Standard Time (four hours behind), and, for every date, the moonrise, the moonset and the fraction of the moon lit, at 18.10° N, 65.44° W, on the bay.
- Each evening is judged from 6:30 to 10 PM. Out of the sky all evening means below the horizon the whole time. Up all evening means above it the whole time. A crescent row means the moon is up at 6:30 and sets before 10, with the lit fraction the Observatory gives for each date. A moonrise row means it is down at 6:30 and rises before 10.
- The closed nights are the night before, the night of and the night after each full moon, by the date on Vieques.
- The check. All 25 new and full moon times for 2027 agree to within a minute with timeanddate.com’s 2027 moon phase calendar for San Juan, and every new moon date agrees with the separately computed table on the Mosquito Bay page.
