time: add a few more benchmarks

Preparation for upcoming optimizations.

For #63844.

Change-Id: I61803dd8b699e51c391614c99ebbd005df5261cc
Reviewed-on: https://go-review.googlesource.com/c/go/+/586256
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>

src/time/time_test.go

@@ -1539,6 +1539,13 @@ func BenchmarkSecond(b *testing.B) {
 	}
 }
 
+func BenchmarkDate(b *testing.B) {
+	t := Now()
+	for i := 0; i < b.N; i++ {
+		_, _, _ = t.Date()
+	}
+}
+
 func BenchmarkYear(b *testing.B) {
 	t := Now()
 	for i := 0; i < b.N; i++ {
@@ -1546,6 +1553,20 @@ func BenchmarkYear(b *testing.B) {
 	}
 }
 
+func BenchmarkYearDay(b *testing.B) {
+	t := Now()
+	for i := 0; i < b.N; i++ {
+		_ = t.YearDay()
+	}
+}
+
+func BenchmarkMonth(b *testing.B) {
+	t := Now()
+	for i := 0; i < b.N; i++ {
+		_ = t.Month()
+	}
+}
+
 func BenchmarkDay(b *testing.B) {
 	t := Now()
 	for i := 0; i < b.N; i++ {
@@ -1567,6 +1588,14 @@ func BenchmarkGoString(b *testing.B) {
 	}
 }
 
+func BenchmarkDateFunc(b *testing.B) {
+	var t Time
+	for range b.N {
+		t = Date(2020, 8, 22, 11, 27, 43, 123456789, UTC)
+	}
+	_ = t
+}
+
 func BenchmarkUnmarshalText(b *testing.B) {
 	var t Time
 	in := []byte("2020-08-22T11:27:43.123456789-02:00")