
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 IFunction::Monotonicity get(const IDataType & type, const Field & left, const Field & right)
    {
        IFunction::Monotonicity positive{ .is_monotonic = true };
        IFunction::Monotonicity not_monotonic;
        const auto * type_ptr = &type;
        if (const auto * low_cardinality_type = checkAndGetDataType<DataTypeLowCardinality>(type_ptr))
            type_ptr = low_cardinality_type->getDictionaryType().get();
        
        if (checkDataTypes<DataTypeDate, DataTypeDate32, DataTypeDateTime, DataTypeString>(type_ptr))
            return positive;
        if (left.isNull() || right.isNull())
            return {};
        if (left.getType() == Field::Types::UInt64
            && right.getType() == Field::Types::UInt64)
        {
            return (left.get<Int64>() == 0 && right.get<Int64>() == 0)
                || (floor(log10(left.get<UInt64>())) == floor(log10(right.get<UInt64>())))
                ? positive : not_monotonic;
        }
        if (left.getType() == Field::Types::Int64
            && right.getType() == Field::Types::Int64)
        {
            return (left.get<Int64>() == 0 && right.get<Int64>() == 0)
                || (left.get<Int64>() > 0 && right.get<Int64>() > 0 && floor(log10(left.get<Int64>())) == floor(log10(right.get<Int64>())))
                ? positive : not_monotonic;
        }
        return not_monotonic;
    }