来自Flink的官方文件：
https://ci.apache.org/projects/flink/flink-docs-release-1.10/dev/stream/operators/joining.html#interval-加入
示例代码为：

import org.apache.flink.streaming.api.functions.co.ProcessJoinFunction;
import org.apache.flink.streaming.api.windowing.time.Time;

...

val orangeStream: DataStream[Integer] = ...
val greenStream: DataStream[Integer] = ...

orangeStream
    .keyBy(elem => /* select key */)
    .intervalJoin(greenStream.keyBy(elem => /* select key */))
    .between(Time.milliseconds(-2), Time.milliseconds(1))
    .process(new ProcessJoinFunction[Integer, Integer, String] {
        override def processElement(left: Integer, right: Integer, ctx: ProcessJoinFunction[Integer, Integer, String]#Context, out: Collector[String]): Unit = {
         out.collect(left + "," + right); 
        }
      });
    });

从上面的代码中，我想知道如何指定开始时间（例如，从今天开始）来执行这个间隔连接（开始时间之前的数据将不被考虑）。
例如，我已经运行了3天的程序，我不想在3天内对所有数据执行这个连接，我只想对今天生成的数据执行连接。