diff --git a/quickfixj-core/src/main/java/quickfix/DefaultSessionSchedule.java b/quickfixj-core/src/main/java/quickfix/DefaultSessionSchedule.java
index c1ec3e5c4..e2d85ef18 100644
--- a/quickfixj-core/src/main/java/quickfix/DefaultSessionSchedule.java
+++ b/quickfixj-core/src/main/java/quickfix/DefaultSessionSchedule.java
@@ -220,6 +220,8 @@ private TimeInterval theMostRecentIntervalBefore(Calendar t) {
             }
 
         } else {
+            // Note that depending on locale, calling 'set(Calendar.DAY_OF_WEEK, ...)' could result in intervalStart being
+            // a date in the future.
             if (isSet(startTime.getDay())) {
                 intervalStart.set(Calendar.DAY_OF_WEEK, startTime.getDay());
                 if (intervalStart.getTimeInMillis() > t.getTimeInMillis()) {
@@ -236,6 +238,11 @@ private TimeInterval theMostRecentIntervalBefore(Calendar t) {
                 if (intervalEnd.getTimeInMillis() <= intervalStart.getTimeInMillis()) {
                     intervalEnd.add(Calendar.WEEK_OF_MONTH, 1);
                 }
+
+                // in some cases (certain locale), we could run into scenario where the interval end is before the interval start.
+                if (intervalEnd.getTimeInMillis() < intervalStart.getTimeInMillis()) {
+                    intervalEnd.add(Calendar.WEEK_OF_YEAR, 1);
+                }
             } else if (intervalEnd.getTimeInMillis() <= intervalStart.getTimeInMillis()) {
                 intervalEnd.add(Calendar.DAY_OF_WEEK, 1);
             }
diff --git a/quickfixj-core/src/test/java/quickfix/SessionScheduleTest.java b/quickfixj-core/src/test/java/quickfix/SessionScheduleTest.java
index 348c3226d..d024ac432 100644
--- a/quickfixj-core/src/test/java/quickfix/SessionScheduleTest.java
+++ b/quickfixj-core/src/test/java/quickfix/SessionScheduleTest.java
@@ -344,6 +344,31 @@ public void testIsSameSessionWithDay() throws Exception {
         doIsSameSessionTest(schedule, t1, t2, true);
     }
 
+    @Test
+    public void testSessionStartInPreviousDayOfWeek() throws Exception {
+        Locale.setDefault(new Locale("en", "AU"));
+
+        final TimeZone tz = TimeZone.getTimeZone("Australia/Victoria");
+        mockSystemTimeSource.setTime(getTimeStamp(2026, Calendar.FEBRUARY, 23, 10, 0, 0, tz));
+
+        final SessionSettings settings = new SessionSettings();
+        settings.setString(Session.SETTING_START_TIME, "13:00:00 Australia/Victoria");
+
+        // AU week starts on Sunday on Java 17 and below, but on Monday on Java 21 and above (not sure about in between).
+        settings.setString(Session.SETTING_START_DAY, "Sunday");
+
+        settings.setString(Session.SETTING_END_TIME, "17:00:00 America/New_York");
+        settings.setString(Session.SETTING_END_DAY, "Saturday");
+
+        SessionID sessionID = new SessionID("FIX.4.2", "SENDER", "TARGET");
+        final SessionSchedule schedule = new DefaultSessionSchedule(settings, sessionID);
+
+        mockSystemTimeSource
+                .setTime(getTimeStamp(2026, Calendar.FEBRUARY, 23, 10, 0, 0, tz));
+        assertEquals("in session expectation incorrect", true, schedule
+                .isSessionTime());
+    }
+
     @Test
     public void testSettingsWithoutStartEndDay() throws Exception {
         SessionSettings settings = new SessionSettings();