Add ApplicationEvent constructor for specifying timestamp

Closes gh-26871

Author: medwards

spring-context/src/main/java/org/springframework/context/ApplicationEvent.java

@@ -16,6 +16,7 @@
 
 package org.springframework.context;
 
+import java.time.Clock;
 import java.util.EventObject;
 
 /**
@@ -46,6 +47,17 @@ public ApplicationEvent(Object source) {
 		this.timestamp = System.currentTimeMillis();
 	}
 
+	/**
+	 * Create a new {@code ApplicationEvent} with a fixed timestamp.
+	 * @param source the object on which the event initially occurred or with
+	 * which the event is associated (never {@code null})
+	 * @param clock a clock which will provide the timestamp
+	 */
+	public ApplicationEvent(Object source, Clock clock) {
+		super(source);
+		this.timestamp = clock.millis();
+	}
+
 
 	/**
 	 * Return the system time in milliseconds when the event occurred.