Since the start of CET in 1994, our goal was to highlight significant benefits of bedroom dawn simulation, as introduced by the Columbia University chronotherapy group in 1989, following years of research and clinical trials.

Overhead light diffuser used in the earliest dawn-dusk simulation studies, and later by the first home users

The first versions of a dawn simulation system for consumers closely resembled the naturalistic twilight transitions of the outdoors, with gradual, smooth dawn transitions from starlight to sunrise.  It was largely based on the laboratory model (see photos), and it worked successfully in hundreds of bedrooms. However, the device and its placement over the bed was cumbersome, and lamp + control box were expensive. 

A control box set the latitude, longitude and date of the naturalistic twilights

Lighting companies quickly introduced less complex and less expensive models to the market, however they were untested in adequate clinical trials. Just as with miniature light boxes, the manufacturers made ― and still make ― unwarranted claims of efficacy.

When the limited stock of the initial naturalistic dawn-dusk simulator ran out, we selected the simplest ― and one of the least expensive ― commercial alternatives, called the Per2. This model was unique among other “dawn alarm clocks”, which featured gimmicks like sounds and scents that override the circadian rhythm wake-up signal.  When the limited stock of the Per2 ran out in late 2021, the company decided to discontinue production.

The Per2 dawn-dusk simulator

Unfortunately, that currently leaves CET without a dawn (or dawn + dusk) simulator to recommend to our visitors. We urge people to take advantage of the well-established alternative, bright light therapy, until a sufficient twilight system is available to the public. Zeitgeber, an Austrian startup, aims to have a new system completed, tested, and ready for production in 2022, and an official launch and release in early 2023. We look forward to offering it to the CET community as soon as it is ready! If you would like to be added to the list to be notified once it is available, please contact