Yahoo Lifestyle 
Sleep calculator 'predicts' the best time to fall asleep
There is nothing more annoying than setting an alarm for the next morning, only to then watch the last hours of the evening slip by, knowing that if you watch one more episode on Netflix, you're definitely not going to get your eight hours.
When it comes to feeling properly refreshed when you wake up, Hillarys' Sleep Calculator claims to have worked out exactly when you need to be turning off the lights depending on what time you have to get up.
According to the The Sleep Foundation, people wake most refreshed when they wake from REM (Rapid eye movement) Sleep. As such, the calculator, used by UK home decor site Hillarys, proposes bedtimes that fit in with a 90-minute sleep cycle the last stage of which is REM.
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The calculator works by entering a wake up time - whether that's 7am or 10am - for which it then gives you a list of times that would suit you best to fall asleep, factoring in that most people take about 14 minutes to fall asleep.
For example, if your wake up time is 7am, the calculator advises that you're best to head to bed at 9:46pm, 11:16pm, 12:46 am or for extreme night owls, 2:16am.
It is important, however to note that the calculator is simply a guide and isn't endorsed by Australia's Sleep Health Foundation.
In fact on its website, the foundation calls the calculator "unscientific hype" and stresses that it "massively over-generalises".
"There are lots of individual differences in cycle length and the variation may be from around 60 to 110 minutes. There may also be unpredictable differences in the same individual from night-to- night," the foundation wrote, stressing that a regular sleep routine is much more beneficial.
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