Understanding automatic start time adjustment

This article explains the benefits and risks of RaceSplitter’s automatic start time adjustment feature.

Under certain circumstances, RaceSplitter will automatically adjust a race’s start time. This behavior is necessary to allow coaches, who are out on the course, to provide their athletes accurate relative times even when they have started the RaceSplitter timer on their device at some point after the actual start of the race.

On the other hand, this same behavior can be confusing in other circumstances, for example, when timing a wave start race in which a participant starts in a different wave than that which they were originally assigned.

This article attempts to explain this behavior by example:

  1. Imagine that a nordic ski race starts at 9:00:00am, and it’s an interval-start race in which participants are separated by 30 seconds, such that Racer 1 starts at 9:00:00am, Racer 2 starts at 9:00:30, Racer 3 at 9:01:00, and Racer 4 at 9:01:30.
  2. Now let’s imagine there’s a coach who’s stationed out on the course somewhere, waiting for the racer to pass. Since he’s far from the start line, he hasn’t started the timer yet in RaceSplitter on his device.
  3. He sees the first racer, Racer 1, approaching and at this point starts his RaceSplitter timer. Imagine at this point, it’s 10:00:00am.
  4. Racer 1 passes a few seconds later, and the coach records that timing entry at 10:00:05am.
  5. RaceSplitter calculates the Split 1 time for Racer 1 to be 5 seconds, i.e. 10:00:05am minus 10:00:00am.
  6. Racer 4 then passes 20 seconds later. So the coach times Racer 4 at 10:00:25am.
  7. RaceSplitter now needs to calculate the Split 1 time for Racer 4, and this is where things get tricky!
  8. To calculate Racer 4’s first split time, RaceSplitter takes his elapsed time of 25 seconds (i.e. 10:00:25am minus 10:00:00am) and adjusts for his start position, which is known to be 90 seconds behind Racer 1.
  9. That calculation leads to a Split 1 time of negative 65 seconds, i.e. 25 seconds, minus the 90 seconds start offset.
  10. Since negative times don’t physically exist, RaceSplitter’s only option is to adjust the race start clock (on that coach’s device) back by 65 seconds, to 09:58:55am.

This then leads to the following adjustments on Split 1 times:

  • Racer 4: 0 Seconds i.e. 10:00:25am minus the new race start time of 9:58:55am minus 90 seconds start-offset
  • Racer 1: 70 Seconds i.e. 10:00:05am minus 9:58:55am minus 0 seconds start-offset (since he was the first starting racer)

As you can see, when this start-time adjustment happens in RaceSplitter, it affects the split time of all racers.

For coaches, this feature is fantastic, as they are not interested in absolute race times, but rather relative times. In this example, the coach is interested in knowing that even though Racer 1 is still physically ahead of Racer 4 on the course, he’s actually behind Racer 4 by 70 seconds when the start interval adjustment is taken into account.

But for the race organizer of a 10k running event in which waves of 20 participants start in intervals of 5 minutes, this behavior can be terribly confusing. If, for example, a racer programmed to start in wave 8 decides to start in wave 1 (without the organizing knowing and having a chance to update the RaceSplitter), this behavior can lead to a situation such that when that wave-jumping racer is timed, the start time gets adjusted as well as the absolute final times of all other racers.

Beyond the basics

After you've read the Getting Started Tutorial, dive deeper into more advanced topics.

Planning your event

As you plan the timing of your first event, here's what you'll want to think about.

Start types

RaceSplitter supports four race start types — mass, interval, wave and variable.


While the RaceSplitter app supports a single user-defined field, complex categorization is supported at the RaceSplitter website.



This article explains how to publish, export and edit your results, both in the app and online.

Multiple Devices

Easily time intermediate points on the course, with RaceSplitter's multi-device support.

Auto-split Mode

Auto-split mode is useful for timing multi-lap races, but should be disabled for most others.

Bibless timing

This article explains how to create timing entries in rapid-fire mode without entering bib numbers.

The Timing Bar

The RaceSplitter "timing bar" allows you to assign the same time to multiple racers — useful when timing groups of people arriving together.

Racer Compensation

RaceSplitter supports the application of compensation factors in adaptive and handicap sports.

Automatic start time adjustment

Under certain circumstances, RaceSplitter will automatically adjust the race start time. This is both a benefit, and a risk.

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