diff --git a/src/time/format.go b/src/time/format.go
index 9beb5d9a48..899b6a40b0 100644
--- a/src/time/format.go
+++ b/src/time/format.go
@@ -1112,7 +1112,7 @@ func parse(layout, value string, defaultLocation, local *Location) (Time, error)
 			return Time{}, &ParseError{alayout, avalue, "", value, ": day-of-year out of range"}
 		}
 		if m == 0 {
-			m = yday/31 + 1
+			m = (yday-1)/31 + 1
 			if int(daysBefore[m]) < yday {
 				m++
 			}
diff --git a/src/time/format_test.go b/src/time/format_test.go
index 34990cdbc3..a030242e6a 100644
--- a/src/time/format_test.go
+++ b/src/time/format_test.go
@@ -756,3 +756,17 @@ func TestParseMonthOutOfRange(t *testing.T) {
 		}
 	}
 }
+
+// Issue 37387.
+func TestParseYday(t *testing.T) {
+	t.Parallel()
+	for i := 1; i <= 365; i++ {
+		d := fmt.Sprintf("2020-%03d", i)
+		tm, err := Parse("2006-002", d)
+		if err != nil {
+			t.Errorf("unexpected error for %s: %v", d, err)
+		} else if tm.Year() != 2020 || tm.YearDay() != i {
+			t.Errorf("got year %d yearday %d, want %d %d", tm.Year(), tm.YearDay(), 2020, i)
+		}
+	}
+}