Fix milestone due date

Closes gh-31

core/src/main/java/io/spring/release/SpringReleases.java

@@ -331,8 +331,8 @@ public void scheduleReleaseIfNotExists(String owner, String repo, String version
 		var releaseTrainSpec = SpringReleaseTrainSpec.builder()
 				.nextTrain()
 				.version(baseVersion)
-				.weekOfMonth(dayOfWeek)
-				.dayOfWeek(weekOfMonth)
+				.weekOfMonth(weekOfMonth)
+				.dayOfWeek(dayOfWeek)
 				.build();
 		// @formatter:on
 

core/src/test/java/io/spring/release/SpringReleasesTests.java

@@ -18,6 +18,7 @@
 
 import java.time.Instant;
 import java.time.LocalDate;
+import java.time.LocalTime;
 import java.time.ZoneOffset;
 import java.time.temporal.ChronoUnit;
 import java.util.ArrayList;
@@ -55,6 +56,10 @@ public class SpringReleasesTests {
 
 	private static final String REPO = "spring-security";
 
+	private static final int WEEK_OF_MONTH = 3;
+
+	private static final int DAY_OF_WEEK = 1;
+
 	// @formatter:off
 	private static final List<Milestone> MILESTONES = List.of(new Milestone("6.0.4", 6L, toInstant("2023-06-19")),
 			new Milestone("6.1.x", 100L, null),
@@ -558,6 +563,35 @@ public void scheduleReleaseIfNotExistsWhenSnapshotVersionExistsThenNotCreated()
 		assertThat(repository.name()).isEqualTo(REPO);
 	}
 
+	// gh-31
+	@Test
+	public void scheduleReleaseIfNotExistsWhenCreatedThenDueOnCorrectDate() {
+		var version = "6.1.9";
+		this.springReleases.scheduleReleaseIfNotExists(OWNER, REPO, version, WEEK_OF_MONTH, DAY_OF_WEEK);
+
+		var repositoryCaptor = forClass(Repository.class);
+		var milestoneCaptor = forClass(Milestone.class);
+		verify(this.gitHubApi).getMilestone(repositoryCaptor.capture(), eq(version));
+
+		var repository = repositoryCaptor.getValue();
+		assertThat(repository.owner()).isEqualTo(OWNER);
+		assertThat(repository.name()).isEqualTo(REPO);
+		verify(this.gitHubApi).createMilestone(eq(repository), milestoneCaptor.capture());
+
+		var releaseTrainSpec = SpringReleaseTrainSpec.builder()
+			.nextTrain()
+			.version(version)
+			.weekOfMonth(WEEK_OF_MONTH)
+			.dayOfWeek(DAY_OF_WEEK)
+			.build();
+		var releaseTrain = new SpringReleaseTrain(releaseTrainSpec);
+		var nextReleaseDate = releaseTrain.getNextReleaseDate(LocalDate.now());
+		var dueOn = nextReleaseDate.atTime(LocalTime.NOON).toInstant(ZoneOffset.UTC);
+		var milestone = milestoneCaptor.getValue();
+		assertThat(milestone.title()).isEqualTo(version);
+		assertThat(milestone.dueOn()).isEqualTo(dueOn);
+	}
+
 	private static Instant toInstant(String date) {
 		return LocalDate.parse(date).atStartOfDay().toInstant(ZoneOffset.UTC);
 	}