
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
inline DateTime64::NativeType execute(UInt16 d, const DateLUTImpl & time_zone) const
    {
        const auto dt = ToDateTimeImpl::execute(d, time_zone);
        return execute(dt, time_zone);
    }
    inline DateTime64::NativeType execute(Int32 d, const DateLUTImpl & time_zone) const
    {
        const auto dt = time_zone.fromDayNum(ExtendedDayNum(d));
        return DecimalUtils::decimalFromComponentsWithMultiplier<DateTime64>(dt, 0, scale_multiplier);
    }
    inline DateTime64::NativeType execute(UInt32 dt, const DateLUTImpl & ) const
    {
        return DecimalUtils::decimalFromComponentsWithMultiplier<DateTime64>(dt, 0, scale_multiplier);
    }
};
/** Conversion of Date or DateTime to DateTime64: add zero sub-second part.
  */
template <typename Name> struct ConvertImpl<DataTypeDate, DataTypeDateTime64, Name, ConvertDefaultBehaviorTag>
    : DateTimeTransformImpl<DataTypeDate, DataTypeDateTime64, ToDateTime64Transform> {};
template <typename Name> struct ConvertImpl<DataTypeDate32, DataTypeDateTime64, Name, ConvertDefaultBehaviorTag>
    : DateTimeTransformImpl<DataTypeDate32, DataTypeDateTime64, ToDateTime64Transform> {};
template <typename Name> struct ConvertImpl<DataTypeDateTime, DataTypeDateTime64, Name, ConvertDefaultBehaviorTag>
    : DateTimeTransformImpl<DataTypeDateTime, DataTypeDateTime64, ToDateTime64Transform> {};
/** Transformation of numbers, dates, datetimes to strings: through formatting.
  */
template <typename DataType>
struct FormatImpl
{
    template <typename ReturnType = void>
    static ReturnType execute(const typename DataType::FieldType x, WriteBuffer & wb, const DataType *, const DateLUTImpl *)