diff --git a/postgres.go b/postgres.go
index c0fdea0..7c59701 100644
--- a/postgres.go
+++ b/postgres.go
@@ -165,11 +165,11 @@ func (dialector Dialector) DataTypeOf(field *schema.Field) string {
 		} else {
 			switch {
 			case size <= 16:
-				return "smallint"
+				return "int2"
 			case size <= 32:
-				return "integer"
+				return "int4"
 			default:
-				return "bigint"
+				return "int8"
 			}
 		}
 	case schema.Float:
@@ -186,7 +186,8 @@ func (dialector Dialector) DataTypeOf(field *schema.Field) string {
 		}
 		return "text"
 	case schema.Time:
-		if field.Precision > 0 {
+		// in postgresql, Precision == 0, This means being accurate to the seconds.
+		if field.Precision >= 0 && field.Precision <= 6 {
 			return fmt.Sprintf("timestamptz(%d)", field.Precision)
 		}
 		return "timestamptz"
@@ -210,11 +211,11 @@ func (dialectopr Dialector) RollbackTo(tx *gorm.DB, name string) error {
 func getSerialDatabaseType(s string) (dbType string, ok bool) {
 	switch s {
 	case "smallserial":
-		return "smallint", true
+		return "int2", true
 	case "serial":
-		return "integer", true
+		return "int4", true
 	case "bigserial":
-		return "bigint", true
+		return "int8", true
 	default:
 		return "", false
 	}