Include average go-to-sleep and wake up times to help make sense of (and manage) sleep irregularity info

From Chris Ball on 2017/10/22 07:45:43 +0000

Very difficult to make sense of present sleep irregularity chart and stats. I work shifts so will always struggle to improve irregularity but, when off work, could benefit from knowing where the mid-point is when going to sleep and waking up.

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