Test an earlier caffeine cutoff.

For your baseline, note the last caffeinated drink, an approximate amount if known and your morning rested rating. Include tea, energy drinks and other caffeine sources rather than treating coffee as the entire picture. If you do not know the amount, keep that uncertainty instead of assigning a precise dose from an unrelated café or product.

Choose a reasonably typical period. A baseline collected during travel or an unusually demanding week may not represent the routine you intend to compare. Keep a short note of those circumstances. You are trying to understand your own pattern, so a clear account of the baseline matters more than a visually complete calendar.

Write an earlier last-drink time that is realistic for your schedule and the question you want to ask. A clock time can be convenient for a regular routine; shift work may need a different plan with professional guidance. Do not adopt someone else's afternoon rule when their bedtime, work or caffeine routine differs from yours.

Be explicit about whether you are moving a drink earlier, reducing the amount or both. Those are different changes. Do not increase your total caffeine just to keep a comparison tidy. If caffeine affects a health condition or medicine, or changing intake causes problems, seek individual advice rather than forcing the experiment to continue as written.

Keep the morning check-in brief and record whether you actually followed the cutoff. A late drink does not erase the week; it changes how that night's observation should be described. Missing, followed and not-followed are different states. Do not silently count a missing answer as successful adherence just because nothing was logged.

Keep other major changes visible: late work, illness, travel, a new bedtime or a new exercise schedule. Do not deliberately preserve an unhealthy habit for cleaner data. If several things change at once, write that the result cannot isolate caffeine timing. A clear limitation is more useful than an impressive but misleading improvement percentage.

A half-life calculator estimates how a logged dose may decline under an assumed clearance rate. It does not measure caffeine in your blood or predict your rested answer. Use it to understand the question, then compare the outcome you chose in advance: how rested you felt across the collected mornings.

Check the size and consistency of any difference, the number of usable entries and how practical the habit was. Better, worse and unclear are all possible. A before-and-after result is still vulnerable to expectations and changing circumstances. If the difference is small or the periods were very different, leave the answer open instead of presenting the plan as proven.

Perkly focuses on drink logging, estimated caffeine decay and a last-call reminder. Night Lab is being built around rested mornings and one sleep habit experiment at a time. The products answer related questions without making an estimated caffeine curve the same thing as evidence that your sleep improved. Night Lab's public App Store release is pending.

You can run the observation on paper now and use the existing calculator without an account. If persistent sleep problems or excessive sleepiness remain, seek professional assessment rather than repeatedly moving the cutoff earlier. A caffeine diary is useful context for that conversation; it is not a substitute for identifying other causes.