A reader asks:

With last Saturday’s switch to Daylight Saving time, I assumed I would stop awakening one hour before my 5:00 a.m. alarm. However, I still awaken at 4:00 a.m. My bedtime is 10 p.m., and I use a light box recommended by CET for thirty minutes upon awakening. I also frequently nod off at night around 8 p.m. while watching TV, which using the light box a second time in the evening did not fix. Any help would be appreciated. Thank you!

Answer:

It seems you are definitely a lark (as opposed to a night owl), but you want to wake up a little later than you do, and stay up a little later.
In that case, we would recommend that you stop using a light box in the morning, since that will reinforce an early morning hour as your default range of times for beginning your day.

Instead, begin using the light box again in the evening, but slightly earlier than you did before. For example, if you start to nod off at around 8 pm, you might want to use the light box for thirty minutes beginning at about 7:30 pm.
This might correct the problem in as little as a day or two; if not, continue this routine for a week. As soon as your inner clock has been reset, you may stop using the light box in the evening, and go back to using it in the morning if you depressed.
Record the time you wake up and go to bed to see whether these exposures make it easier for you to stay up later, or get up later.
You can also keep the light out of your bedroom until you are ready to get up, and make sure your environment in the evening (until two hours before you want to go to sleep) is light.