Sleep
3 tools 2 articles
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Tools3
RT-HLT-019 Caffeine Half-Life Calculator
Decay tracker + sleep cutoff
Health & Fitness
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RT-FDT-010 Jet-Lag Calculator
How many days the body clock takes to close a clock difference, both ways round, at the published averages
Food & Travel
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RT-HLT-007 Sleep Calculator
Find the best times to wake up or go to sleep based on 90-minute sleep cycles — wake up refreshed, not groggy.
Health & Fitness
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Articles2
Three Lux at Night, and a Thicker Heart Wall Three Years Later
Eleven thousand people wore light sensors for a week and had their hearts scanned three years on. The brighter...
AM
14 Sep
Sleep Cycles and the 90-Minute Rule: What the Science Actually Says (2026)
Two NIH institutes give two different sleep-cycle lengths, and neither is a fixed 90 minutes. What the primary...
AM
21 Jul
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