ZmanimFormatter.formatInstant: format in the ZoneId passed in

src/main/java/com/kosherjava/zmanim/util/ZmanimFormatter.java

@@ -259,16 +259,18 @@ public String format(Duration duration) {
 	}
 
 	/**
-	 * Formats an {@link Instant} using this class's {@link #getDateTimeFormatter()}.
+	 * Formats an {@link Instant} in the given {@link ZoneId} using this class's {@link #getDateTimeFormatter()}.
 	 * 
 	 * @param instant the {@code Instant} to format.
-	 * @param zoneId the {@link ZoneId} used to help format based on the {@code Instant}'s DST and other settings.
+	 * @param zoneId the {@link ZoneId} to format the {@code Instant} in (including its DST and other settings).
 	 * @return the formatted String
 	 * @see #formatXSDateTime(Instant)
 	 */
 	public String formatInstant(Instant instant, ZoneId zoneId) {
 		ZonedDateTime dateTime = instant.atZone(zoneId);
-		return this.getDateTimeFormatter().format(dateTime);
+		// The formatter has this ZmanimFormatter's zone as its override zone (see the constructor), and an override zone converts
+		// the ZonedDateTime back to that zone, so it has to be replaced by the requested one.
+		return this.getDateTimeFormatter().withZone(zoneId).format(dateTime);
 	}
 
 	/**

src/test/java/com/kosherjava/zmanim/util/ZmanimFormatterFormatInstantTest.java

@@ -0,0 +1,46 @@
+/*
+ * Zmanim Java API
+ * Copyright © 2004-2026 Eliyahu Hershfeld
+ *
+ * This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General
+ * Public License as published by the Free Software Foundation; version 2.1 of the License.
+ *
+ * This library is distributed in the hope that it will be useful,but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
+ * details.
+ * You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA,
+ * or connect to: https://www.gnu.org/licenses/old-licenses/lgpl-2.1.html
+ */
+package com.kosherjava.zmanim.util;
+
+import static org.junit.Assert.assertEquals;
+
+import java.time.Instant;
+import java.time.ZoneId;
+import java.time.format.DateTimeFormatter;
+
+import org.junit.Test;
+
+/**
+ * {@link ZmanimFormatter#formatInstant(Instant, ZoneId)} must format in the {@code ZoneId} passed to it, not in the formatter's
+ * own zone.
+ */
+public class ZmanimFormatterFormatInstantTest {
+	private static final Instant INSTANT = Instant.parse("2020-03-25T21:37:09Z");
+
+	@Test
+	public void formatsInTheRequestedZone() {
+		ZmanimFormatter formatter = new ZmanimFormatter(ZoneId.of("UTC"));
+		assertEquals("9:37:09", formatter.formatInstant(INSTANT, ZoneId.of("UTC")));
+		assertEquals("5:37:09", formatter.formatInstant(INSTANT, ZoneId.of("America/New_York"))); // EDT, UTC-4
+		assertEquals("11:37:09", formatter.formatInstant(INSTANT, ZoneId.of("Pacific/Kiritimati"))); // UTC+14, the next day
+	}
+
+	@Test
+	public void worksWithAFormatterSetWithoutAZone() {
+		ZmanimFormatter formatter = new ZmanimFormatter(ZoneId.of("UTC"));
+		formatter.setDateTimeFormatter(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm"));
+		assertEquals("2020-03-26 08:37", formatter.formatInstant(INSTANT, ZoneId.of("Australia/Sydney"))); // AEDT, UTC+11
+	}
+}