`select parseDateTimeBestEffort('01/12/2017, 18:31:44')`

It is confused by a comma - should be easy to fix.
{
                    using FractionalType = typename std::decay<decltype(fractional->value)>::type;
                    
                    
                    
                    num_digits = std::min(static_cast<size_t>(std::numeric_limits<FractionalType>::digits10), num_digits);
                    fractional->digits = num_digits;
                    readDecimalNumber(fractional->value, num_digits, digits);
                }
            }
            else if (c == '+' || c == '-')
            {
                ++in.position();
                num_digits = readDigits(digits, sizeof(digits), in);
                if (num_digits == 6 && !has_time && year && month && day_of_month)
                {
                    
                    readDecimalNumber<2>(hour, digits);
                    readDecimalNumber<2>(minute, digits + 2);
                    readDecimalNumber<2>(second, digits + 4);
                    has_time = true;
                }
                else
                {
                    
                    has_time_zone_offset = true;
                    if (c == '-')
                        time_zone_offset_negative = true;
                    if (num_digits == 4)
                    {