
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
const IColumn & column_from,
        IColumn & column_to,
        const ISerialization & serialization_from,
        size_t input_rows_count,
        const PaddedPODArray<UInt8> * null_map = nullptr,
        const IDataType * result_type = nullptr)
    {
        static_assert(std::is_same_v<StringColumnType, ColumnString> || std::is_same_v<StringColumnType, ColumnFixedString>,
                "Can be used only to parse from ColumnString or ColumnFixedString");
        if (const StringColumnType * col_from_string = checkAndGetColumn<StringColumnType>(&column_from))
        {
            column_to.reserve(input_rows_count);
            FormatSettings format_settings;
            for (size_t i = 0; i < input_rows_count; ++i)
            {
                if (null_map && (*null_map)[i])
                {
                    column_to.insertDefault();
                    continue;
                }
                const auto & val = col_from_string->getDataAt(i);
                ReadBufferFromMemory read_buffer(val.data, val.size);
                serialization_from.deserializeWholeText(column_to, read_buffer, format_settings);