
select toDateTime64(-86400 ,9,'UTC') ==  1969-12-31 00:00:00.000000000

select toDateTime64(-86400.00 ,9,'UTC') ==  1970-01-01 00:00:00.000000000 


However, I expect both outputs to be same. 

Version affected : 22.8
safe_convert_custom_types = to_type->getCustomName() && from_type_custom_name->getName() == to_type->getCustomName()->getName();
        if (from_type->equals(*to_type) && safe_convert_custom_types)
            return createIdentityWrapper(from_type);
        else if (WhichDataType(from_type).isNothing())
            return createNothingWrapper(to_type.get());
        WrapperType ret;
        auto make_default_wrapper = [&](const auto & types) -> bool
        {
            using Types = std::decay_t<decltype(types)>;
            using ToDataType = typename Types::LeftType;
            if constexpr (
                std::is_same_v<ToDataType, DataTypeUInt16> ||
                std::is_same_v<ToDataType, DataTypeUInt32> ||
                std::is_same_v<ToDataType, DataTypeUInt64> ||
                std::is_same_v<ToDataType, DataTypeUInt128> ||
                std::is_same_v<ToDataType, DataTypeUInt256> ||
                std::is_same_v<ToDataType, DataTypeInt8> ||
                std::is_same_v<ToDataType, DataTypeInt16> ||
                std::is_same_v<ToDataType, DataTypeInt32> ||
                std::is_same_v<ToDataType, DataTypeInt64> ||
                std::is_same_v<ToDataType, DataTypeInt128> ||
                std::is_same_v<ToDataType, DataTypeInt256> ||
                std::is_same_v<ToDataType, DataTypeFloat32> ||
                std::is_same_v<ToDataType, DataTypeFloat64> ||
                std::is_same_v<ToDataType, DataTypeDate> ||
                std::is_same_v<ToDataType, DataTypeDate32> ||
                std::is_same_v<ToDataType, DataTypeDateTime> ||
                std::is_same_v<ToDataType, DataTypeUUID>)
            {
                ret = createWrapper(from_type, checkAndGetDataType<ToDataType>(to_type.get()), requested_result_is_nullable);