
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
{
    static constexpr auto name = "toDateTime64";
    const DateTime64::NativeType scale_multiplier = 1;
    ToDateTime64TransformUnsigned(UInt32 scale = 0) 
        : scale_multiplier(DecimalUtils::scaleMultiplier<DateTime64::NativeType>(scale))
    {}
    inline NO_SANITIZE_UNDEFINED DateTime64::NativeType execute(FromType from, const DateLUTImpl &) const
    {
        from = std::min<time_t>(from, LUT_MAX_TIME);
        return DecimalUtils::decimalFromComponentsWithMultiplier<DateTime64>(from, 0, scale_multiplier);
    }
};
template <typename FromType>
struct ToDateTime64TransformSigned
{
    static constexpr auto name = "toDateTime64";
    const DateTime64::NativeType scale_multiplier = 1;
    ToDateTime64TransformSigned(UInt32 scale = 0) 
        : scale_multiplier(DecimalUtils::scaleMultiplier<DateTime64::NativeType>(scale))
    {}
    inline NO_SANITIZE_UNDEFINED DateTime64::NativeType execute(FromType from, const DateLUTImpl &) const
    {
        from = std::max<time_t>(from, LUT_MIN_TIME);
        from = std::min<time_t>(from, LUT_MAX_TIME);