tmtime: Canonical, some comments (#2312)

types/canonical_json.go

@@ -4,6 +4,7 @@ import (
 	"time"
 
 	cmn "github.com/tendermint/tendermint/libs/common"
+	tmtime "github.com/tendermint/tendermint/types/time"
 )
 
 // Canonical json is amino's json for structs with fields in alphabetical order
@@ -110,5 +111,5 @@ func CanonicalTime(t time.Time) string {
 	// Note that sending time over amino resets it to
 	// local time, we need to force UTC here, so the
 	// signatures match
-	return t.Round(0).UTC().Format(TimeFormat)
+	return tmtime.Canonical(t).Format(TimeFormat)
 }

types/genesis.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/tendermint/tendermint/crypto"
 	cmn "github.com/tendermint/tendermint/libs/common"
+	tmtime "github.com/tendermint/tendermint/types/time"
 )
 
 const (
@@ -79,7 +80,7 @@ func (genDoc *GenesisDoc) ValidateAndComplete() error {
 	}
 
 	if genDoc.GenesisTime.IsZero() {
-		genDoc.GenesisTime = time.Now()
+		genDoc.GenesisTime = tmtime.Now()
 	}
 
 	return nil

types/protobuf_test.go

@@ -9,6 +9,7 @@ import (
 	"github.com/tendermint/tendermint/crypto"
 	"github.com/tendermint/tendermint/crypto/ed25519"
 	"github.com/tendermint/tendermint/crypto/secp256k1"
+	tmtime "github.com/tendermint/tendermint/types/time"
 )
 
 func TestABCIPubKey(t *testing.T) {
@@ -77,7 +78,7 @@ func TestABCIConsensusParams(t *testing.T) {
 func TestABCIHeader(t *testing.T) {
 	header := &Header{
 		Height:          int64(3),
-		Time:            time.Now(),
+		Time:            tmtime.Now(),
 		NumTxs:          int64(10),
 		ProposerAddress: []byte("cloak"),
 	}

types/time/time.go

@@ -5,16 +5,23 @@ import (
 	"time"
 )
 
-// Now returns UTC time rounded since the zero time.
+// Now returns the current time in UTC with no monotonic component.
 func Now() time.Time {
-	return time.Now().Round(0).UTC()
+	return Canonical(time.Now())
 }
 
+// Canonical returns UTC time with no monotonic component.
+func Canonical(t time.Time) time.Time {
+	return t.Round(0).UTC()
+}
+
+// WeightedTime for computing a median.
 type WeightedTime struct {
 	Time   time.Time
 	Weight int64
 }
 
+// NewWeightedTime with time and weight.
 func NewWeightedTime(time time.Time, weight int64) *WeightedTime {
 	return &WeightedTime{
 		Time:   time,