framework/db/mysql/QueryBuilder.php
private function defaultTimeTypeMap()
    {
        $map = [
            Schema::TYPE_DATETIME => 'datetime',
            Schema::TYPE_TIMESTAMP => 'timestamp',
            Schema::TYPE_TIME => 'time',
        ];

        if ($this->supportsFractionalSeconds()) {
            $map = [
                Schema::TYPE_DATETIME => 'datetime(0)',
                Schema::TYPE_TIMESTAMP => 'timestamp(0)',
                Schema::TYPE_TIME => 'time(0)',
            ];
        }

        return $map;
    }
private function defaultTimeTypeMap()
    {
        $map = [
            Schema::TYPE_DATETIME => 'datetime',
            Schema::TYPE_TIMESTAMP => 'timestamp',
            Schema::TYPE_TIME => 'time',
        ];

        if ($this->supportsFractionalSeconds()) {
            $map = [
                Schema::TYPE_DATETIME => 'datetime(0)',
                Schema::TYPE_TIMESTAMP => 'timestamp(0)',
                Schema::TYPE_TIME => 'time(0)',
            ];
        }

        return $map;
    }
Returns the map for default time type.
If the version of MySQL is lower than 5.6.4, then the types will be without fractional seconds,
otherwise with fractional seconds.

@return array