From 67cae348ece850b7e89f58714c5c4f9a4f651d5a Mon Sep 17 00:00:00 2001
From: Kirk Shoop <kirk.shoop@microsoft.com>
Date: Tue, 6 May 2014 07:57:35 -0700
Subject: [PATCH] fix to remove drift from schedulePeriodic

---
 rxjava-core/src/main/java/rx/Scheduler.java | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/rxjava-core/src/main/java/rx/Scheduler.java b/rxjava-core/src/main/java/rx/Scheduler.java
index 1d45006649..2aa3017476 100644
--- a/rxjava-core/src/main/java/rx/Scheduler.java
+++ b/rxjava-core/src/main/java/rx/Scheduler.java
@@ -99,15 +99,16 @@ public abstract static class Worker implements Subscription {
          */
         public Subscription schedulePeriodically(final Action0 action, long initialDelay, long period, TimeUnit unit) {
             final long periodInNanos = unit.toNanos(period);
+            final long startInNanos = TimeUnit.MILLISECONDS.toNanos(now()) + unit.toNanos(initialDelay);
 
             final Action0 recursiveAction = new Action0() {
+                long count = 0;
                 @Override
                 public void call() {
                     if (!isUnsubscribed()) {
-                        long startedAt = now();
                         action.call();
-                        long timeTakenByActionInNanos = TimeUnit.MILLISECONDS.toNanos(now() - startedAt);
-                        schedule(this, periodInNanos - timeTakenByActionInNanos, TimeUnit.NANOSECONDS);
+                        long nextTick = startInNanos + (++count * periodInNanos);
+                        schedule(this, nextTick - TimeUnit.MILLISECONDS.toNanos(now()), TimeUnit.NANOSECONDS);
                     }
                 }
             };