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 │
└───────────────────────────────────────┘
```
|| std::is_same_v<ToDataType, DataTypeDateTime>
            
            || std::is_same_v<ToDataType, DataTypeDateTime64>)
        {
            optional_args.push_back({"timezone", &isString, &isColumnConst, "const String"});
        }
        validateFunctionArgumentTypes(*this, arguments, mandatory_args, optional_args);
        if constexpr (std::is_same_v<ToDataType, DataTypeInterval>)
        {
            return std::make_shared<DataTypeInterval>(Name::kind);
        }
        else if constexpr (to_decimal)
        {
            UInt64 scale = extractToDecimalScale(arguments[1]);
            if constexpr (std::is_same_v<Name, NameToDecimal32>)
                return createDecimalMaxPrecision<Decimal32>(scale);
            else if constexpr (std::is_same_v<Name, NameToDecimal64>)
                return createDecimalMaxPrecision<Decimal64>(scale);
            else if constexpr (std::is_same_v<Name, NameToDecimal128>)
                return createDecimalMaxPrecision<Decimal128>(scale);
            else if constexpr (std::is_same_v<Name, NameToDecimal256>)
                return createDecimalMaxPrecision<Decimal256>(scale);
            throw Exception("Unexpected branch in code of conversion function: it is a bug.", ErrorCodes::LOGICAL_ERROR);
        }
        else
        {
            
            UInt8 timezone_arg_position = 1;
            UInt32 scale [[maybe_unused]] = DataTypeDateTime64::default_scale;