NEW YORK —Wednesday and Saturday are Konstantin Augemberg’s favorite days. But on Thursday, he’s always a bit sad. His ideal bedtime is exactly between 10:15 p.m. and 10:30 p.m. And if he walks his dogin the morning, his mood is better for the rest of the day.

He discovered these particularities about himself by measuring — three times a day — some 20 physiological and psychological parameters, including his weight, the exercises he’d done, his heart rate, his mood and what he’d eaten. “I started doing this five or six years ago,” he says. “My whole life is entirely quantified with numbers.”

Augemberg regards himself as a lifelogger, one of a tribe of technophiles who methodically register and publish each of their comings and goings with digital tools. He uses several mobile applications such as the data tracker rTracker and body monitors such as BodyMedia or the headband Zeo and personal notes. “I use this information to establish correlations between certain kinds of behavior and my physical and mental state,” he says. “All this helps me to improve my everyday life.”

All the data is then published on his blog, Measuredme.com, where anyone can download all the information. “I can go back in time, see my physical or health state three months ago,” he says while pointing at a chart on his phone. There was a low point around June 22. “I was very sick that day,” he says.

Augemberg believes that this constant auto-quantification has made him more aware of his own feelings and better at interpreting others’. “Right now, for example, I feel quite stressed ... but happy though.”

Who are these people?

The first lifeloggers appeared in the 1990s. Steve Mann, professor at the University of Toronto’s Department of Applied Sciences, wore a video camera on his head for a year. “From 1994 to 1995, I streamed in live the information filmed and put it on a web page,” he says. “Internet users were able to see through my eyes and could even change the settings of my field of vision.”

In 2004, Microsoft engineer Gordon Bellput all of his books, CDs, films, emails — even the web pages he browsed or produced — online for the world to see. It was part of a research project called MyLifeBits that aimed to collect a lifetime of storage about Bell.

But the movement really began to take off in 2008, when supporters of auto-quantification got together in Mountain View, California. “One year later, we launched our first meeting in New York,” says Steven Dean, who organizes the meetings every two months. “We have more than 2,200 members today from Boston, London, Amsterdam and Canada.”

The advent of smartphonesand apps really changed the movement by making data tracking easier. “People are not always next to their computer, but they always have their phone with them,” Dean says. Nowadays, you can download apps that count the number of steps you’ve taken during the day, measure the vibrations of your mattress to see the quality of your sleep, or count your calories with photos of your meals.

And let’s not forget all the new gadgets that automatically track personal data — FuelBand, Jawbone and Fitbit as well as the smartwatches, mini and transportable cameras Memoto and SenseCam that take photos every 30 seconds. To say nothing of Google Glasses.

Photo: Quantified Self Institute

Most lifeloggers, including Konstantin Augemberg, are motivated by the desire to optimize their lives, often in a playful way. The graphic designer Nicholas Felton, who created Facebook’s timeline feature, has since 2005 published an annual report identifying all of his activities over the course of the year: his travels, the day when he is most friendly (Monday), his most-worn item of clothing (J-Crew jeans), and even the food he ate the most (pork).

Andrew Paulus, a 24-year-old products manager, realized that he was checking the weather forecast to decide what clothes he was going to wear. “I therefore decided to report on an Excel table how the weather was and the outfits I decided on,” he says. “After a certain time, I noticed the emergence of correlations. Today I don’t even need to think in the morning: I know that when it is more than X °F I wear a T-shirt or, if the risk of rain exceeds a certain percentage, I should take an umbrella.

Why?

For many lifeloggers, auto-quantification is a way of controlling uncertainty in a world increasingly dominated by risk aversion. “It gives me the feeling that I can minimize the unforeseen, that my life depends of my choices rather than God’s will or destiny,” Felton says. “I even measured the consequence of uncertainty on my mood: The more I’m submitted to it, the less happy I am.”

It is also an assurance against oblivion. ”Auto-quantification enables you to create a kind of external memory or black box of your living that captures all your experiences, even the unconscious ones, and allows you to come back to them,” says Abigail Sellen, a Microsoft researcher who studied the uses of the SenseCam. The portable mini-camera was invented by a Microsoft employee after a bike fall she didn’t remember.

But lifelogging isn’t just a lobby created by technophile nerds. Matthew Lee, a researcher at Carnegie Mellon University specializing in human-computer interaction, has used these tools to develop a memory aid for people suffering from Alzheimer's disease. “The idea is to make them wear a video camera and a recording device during the memorable moments of their lives,” Lee says. “Those materials are then handled by software that will spot the most relevant images and sounds to process them into a slide show they could watch on a tablet.” It is about giving the patient the right amount of information to reconstitute memory.

Very early, Steven Dean understood that lifelogging could have health applications. “I grew up with a diabetic sister who measured her glucose rate very morning and an overweight mother who was continuously counting calories,” says Dean. A few years ago, when he began to suffer from eczema on his eyelids, Dean didn’t hesitate. “I started documenting everything ... to keep a detailed logbook of my symptoms, their seriousness and the treatments given,” he recalls.

He then gave all the information to his doctor, who advised him to use diluted bleach on his eyelids. “I immediately noticed that the water had the same smell as in the swimming pools,” Dean says. “And I stopped going to the pool when my problems started.” Chlorine was actually killing his eczema.

“I started swimming again, and everything went back to normal.”