Encode dates in binary format

- Also allow NullTime to handle dates

values.go

@@ -386,9 +386,10 @@ func (n NullBool) Encode(w *WriteBuf, oid Oid) error {
 	return encodeBool(w, n.Bool)
 }
 
-// NullTime represents an bigint that may be null. NullTime implements the
+// NullTime represents an time.Time that may be null. NullTime implements the
 // Scanner and Encoder interfaces so it may be used both as an argument to
-// Query[Row] and a destination for Scan.
+// Query[Row] and a destination for Scan. It corresponds with the PostgreSQL
+// types timestamptz, timestamp, and date.
 //
 // If Valid is false then the value is NULL.
 type NullTime struct {
@@ -398,7 +399,7 @@ type NullTime struct {
 
 func (n *NullTime) Scan(vr *ValueReader) error {
 	oid := vr.Type().DataType
-	if oid != TimestampTzOid && oid != TimestampOid {
+	if oid != TimestampTzOid && oid != TimestampOid && oid != DateOid {
 		return SerializationError(fmt.Sprintf("NullTime.Scan cannot decode OID %d", vr.Type().DataType))
 	}
 
@@ -408,10 +409,13 @@ func (n *NullTime) Scan(vr *ValueReader) error {
 	}
 
 	n.Valid = true
-	if oid == TimestampTzOid {
+	switch oid {
+	case TimestampTzOid:
 		n.Time = decodeTimestampTz(vr)
-	} else {
+	case TimestampOid:
 		n.Time = decodeTimestamp(vr)
+	case DateOid:
+		n.Time = decodeDate(vr)
 	}
 
 	return vr.Err()
@@ -420,7 +424,7 @@ func (n *NullTime) Scan(vr *ValueReader) error {
 func (n NullTime) FormatCode() int16 { return BinaryFormatCode }
 
 func (n NullTime) Encode(w *WriteBuf, oid Oid) error {
-	if oid != TimestampTzOid && oid != TimestampOid {
+	if oid != TimestampTzOid && oid != TimestampOid && oid != DateOid {
 		return SerializationError(fmt.Sprintf("NullTime.Encode cannot encode into OID %d", oid))
 	}
 
@@ -429,10 +433,15 @@ func (n NullTime) Encode(w *WriteBuf, oid Oid) error {
 		return nil
 	}
 
-	if oid == TimestampTzOid {
+	switch oid {
+	case TimestampTzOid:
 		return encodeTimestampTz(w, n.Time)
-	} else {
+	case TimestampOid:
 		return encodeTimestamp(w, n.Time)
+	case DateOid:
+		return encodeDate(w, n.Time)
+	default:
+		panic("unreachable")
 	}
 }
 
@@ -1055,8 +1064,16 @@ func encodeDate(w *WriteBuf, value interface{}) error {
 		return fmt.Errorf("Expected time.Time, received %T", value)
 	}
 
-	s := t.Format("2006-01-02")
-	return encodeText(w, s)
+	tUnix := time.Date(t.Year(), t.Month(), t.Day(), 0, 0, 0, 0, time.UTC).Unix()
+	dateEpoch := time.Date(2000, 1, 1, 0, 0, 0, 0, time.UTC).Unix()
+
+	secSinceDateEpoch := tUnix - dateEpoch
+	daysSinceDateEpoch := secSinceDateEpoch / 86400
+
+	w.WriteInt32(4)
+	w.WriteInt32(int32(daysSinceDateEpoch))
+
+	return nil
 }
 
 const microsecFromUnixEpochToY2K = 946684800 * 1000000