WATERLOO - The beginning of Daylight Saving Time could mean some groggy people hitting the streets Monday morning.

Daylight Saving Time, which begins at 2 a.m. Sunday, effectively shifts one hour of daylight from the morning to the evening, allowing most residents across the United States to better enjoy their summer days. Only two regions - Arizona and part of Indiana - do not observe the change.

While most people find changing all the clocks in their house a nuisance and the hour of missed sleep each spring a drag, they can't help but enjoy the extra hour of sunlight each summer night or the extra hour of sleep every October.

But the most difficult adjustment is aligning the internal clock with the new external cues. Dr. Harbhajan Singh, a sleep medicine specialist at Covenant Medical Center, said a person's internal clock runs on a 25-hour schedule. Without external cues, like light and meal times, Singh said a person would go to sleep one hour later and wake up one hour later each day.

"Light is the biggest thing that keeps us on a 24-hour clock. The best thing to do … is to get up and get exposed to light," said Singh. "That sets the internal clock to an earlier time. We are training our internal clock to the outside clock."

Steven Rondorf, program coordinator at the Allen Sleep Center, said changing bedtime habits throughout the week can make the overnight transition easier to manage. He recommends putting children to bed about 15 to 20 minutes earlier each night.

"Adolescents and teens, their clocks are already skewed. They don't want to get up in the morning and they stay up later at night," Rondorf said. "Their clocks will be even more skewed because we are asking them to get up earlier."

Even if everyone catches up on that one missed hour between Saturday and Sunday, Rondorf said the underlying problem will still be unsolved.

"We are living in a society where we don't get enough sleep," he said. "It shows itself with excessive daytime sleepiness. This is a good time to remind people of good sleeping habits."

Rondorf recommends keeping a regular sleep schedule, even on weekends, unless you aren't getting enough sleep during the week. Then weekends are a great time to get rid of some of the bags under your eyes. Another point of good sleep hygiene is to reduce caffeine and alcohol intake before bed and start soothing rituals, like taking a hot bath to calm your nerves.

"I always compare sleep deprivation to credit card debt. We build up that sleep debt during the week, but you can pay it off on the weekend," he said. "Unfortunately most people end up building up so much debt they can never catch up."

While Americans are dealing with a one-hour change, jet setters often face a bigger problem.

Singh said someone living in the United States and traveling to India, which has a 12-hour time difference, can expect a two- to three-week adjustment period to the new schedule.

"There are some medications that are approved that can help, but those are only used in extreme situations," Singh said.

Emily Christensen can be contacted at (319) 291-1482 or emily.christensen@wcfcourier.com.