21.2:

```
milovidov-desktop :) SELECT CAST(1111111111.222 AS DateTime64(3))

SELECT cast(1111111111.222, 'DateTime64(3)')

Query id: d10c8623-5c74-4a38-b535-a99f6af4d28d

┌─cast(1111111111.222, 'DateTime64(3)')─┐
│               2005-03-18 04:58:31.222 │
└───────────────────────────────────────┘
```

master:

```
milovidov-desktop :) SELECT CAST(1111111111.222 AS DateTime64(3))

SELECT cast(1111111111.222, 'DateTime64(3)')

Query id: cb4af967-a4ae-4df5-89ba-234d68675f93

┌─cast(1111111111.222, 'DateTime64(3)')─┐
│               2005-03-18 04:58:31.000 │
└───────────────────────────────────────┘
```
static IFunction::Monotonicity get(const IDataType & type, const Field & left, const Field & right)
    {
        auto which = WhichDataType(type);
        if (which.isDateOrDateTime() || which.isInt8() || which.isInt16() || which.isUInt8() || which.isUInt16())
            return {true, true, true};
        else if (
            (which.isUInt() && ((left.isNull() || left.get<UInt64>() < 0xFFFF) && (right.isNull() || right.get<UInt64>() >= 0xFFFF)))
            || (which.isInt() && ((left.isNull() || left.get<Int64>() < 0xFFFF) && (right.isNull() || right.get<Int64>() >= 0xFFFF)))
            || (which.isFloat() && ((left.isNull() || left.get<Float64>() < 0xFFFF) && (right.isNull() || right.get<Float64>() >= 0xFFFF)))
            || !type.isValueRepresentedByNumber())
            return {};
        else
            return {true, true, true};
    }
};
struct ToDateTimeMonotonicity
{
    static bool has() { return true; }