That’s an Info level log. It’s not even an error. But it is referring to one of the breaking changes that was announced and there are tons of postings about on the forum. There is no more DateTime. It has been replaced with ZonedDateTime. And the methods on ZonedDateTime have changed slightly. See DateTime Conversion (openHAB 3.x)
That log message is referring to motionTimes so look at the lines that reference that variable. You’ll notice that it’s defined as a Queue<DateTime>. There is no DateTime any more. Now it’s a ZonedDateTime.
Continuing on we see the there is an attempt to call getMillis() on the Object stored by the Queue. That method doesn’t exist on ZonedDateTime. And as far as what’s posted here it’s not even used anyway. Assuming it’s used in that other rule, why use millis? Keep it as a ZonedDateTime and you’ll have a lot more flexibility and the code will be easier to read and understand.