A one-hour change in the alignment between the internal clock and external time can lead to grogginess and reduced performance for one to two days.

“however if you start getting into a habit of going to bed at vastly different times deviating more than or less than one hour from your normal to bedtime well then you're going to start to run into issues such as as waking up feeling groggy even if you got enough sleep so even if you slept the full eight hours that you're used to getting people who go to sleep much later than they normally do or much earlier than they normally do start getting into kind of issues of mood regulation energy regulation not just in the morning but in the afternoon likewise try and wake up at more or less the same time each morning plus or minus one hour that's really going to help you anchor your overall sleep schedule and it's really going to help lead to predictability of your overall levels of energy mood and focus throughout the day”