diff --git a/moshi-adapters/src/main/java/com/squareup/moshi/adapters/Iso8601Utils.kt b/moshi-adapters/src/main/java/com/squareup/moshi/adapters/Iso8601Utils.kt
index 7ba3518aa..99df198b7 100644
--- a/moshi-adapters/src/main/java/com/squareup/moshi/adapters/Iso8601Utils.kt
+++ b/moshi-adapters/src/main/java/com/squareup/moshi/adapters/Iso8601Utils.kt
@@ -125,8 +125,16 @@ internal fun String.parseIsoDate(): Date {
     // if the value has no time component (and no time zone), we are done
     val hasT = readChar(this, offset, 'T')
     if (!hasT && this.length <= offset) {
-      // Note that this uses the host machine's time zone. That's a bug.
-      return GregorianCalendar(year, month - 1, day).time
+      val calendar: Calendar = GregorianCalendar(TIMEZONE_Z, Locale.US)
+      calendar.isLenient = false
+      calendar[Calendar.YEAR] = year
+      calendar[Calendar.MONTH] = month - 1
+      calendar[Calendar.DAY_OF_MONTH] = day
+      calendar[Calendar.HOUR_OF_DAY] = 0
+      calendar[Calendar.MINUTE] = 0
+      calendar[Calendar.SECOND] = 0
+      calendar[Calendar.MILLISECOND] = 0
+      return calendar.time
     }
     if (hasT) {
       offset++
diff --git a/moshi-adapters/src/test/java/com/squareup/moshi/adapters/Rfc3339DateJsonAdapterTest.java b/moshi-adapters/src/test/java/com/squareup/moshi/adapters/Rfc3339DateJsonAdapterTest.java
index 671382066..603565075 100644
--- a/moshi-adapters/src/test/java/com/squareup/moshi/adapters/Rfc3339DateJsonAdapterTest.java
+++ b/moshi-adapters/src/test/java/com/squareup/moshi/adapters/Rfc3339DateJsonAdapterTest.java
@@ -95,7 +95,9 @@ public void variableFractionDigits() throws Exception {
 
   @Test
   public void absentTimeZone() throws Exception {
-    assertThat(adapter.fromJson("\"1970-01-01\"")).isEqualTo(newDateWithHostZone(1970, 1, 1));
+    // A date-only string with no time zone is interpreted as midnight UTC.
+    assertThat(adapter.fromJson("\"1970-01-01\"")).isEqualTo(newDate(1970, 1, 1, 0, 0, 0, 0, 0));
+    assertThat(adapter.fromJson("\"2025-11-20\"")).isEqualTo(newDate(2025, 11, 20, 0, 0, 0, 0, 0));
     assertThat(adapter.fromJson("\"1970-01-01Z\"")).isEqualTo(newDate(1970, 1, 1, 0, 0, 0, 0, 0));
     try {
       adapter.fromJson("\"1970-01-01T00:00:00.000\"");
@@ -112,14 +114,5 @@ private Date newDate(
     return new Date(calendar.getTimeInMillis() - TimeUnit.MINUTES.toMillis(offset));
   }
 
-  /**
-   * Dates specified without any time or timezone (like "1970-01-01") are returned in the host
-   * computer's time zone. This is a longstanding bug that we're attempting to stay consistent with.
-   */
-  private Date newDateWithHostZone(int year, int month, int day) {
-    Calendar calendar = new GregorianCalendar();
-    calendar.set(year, month - 1, day, 0, 0, 0);
-    calendar.set(Calendar.MILLISECOND, 0);
-    return new Date(calendar.getTimeInMillis());
-  }
 }
+