Sleep cycle bedtime calculator

Invalid wake times and out-of-range cycle counts fail clearly with invalid_input instead of inventing a schedule.

How ninety-minute cycles turn a wake time into bedtimes

This calculator models that idea with a fixed cycle length of ninety minutes, returned in the response as cycle_minutes so clients never have to hard-code the constant. You supply wake_time as a twenty-four-hour HH:MM string such as 07:00 or 06:30. For each cycle count n from the requested maximum down to one, the bedtime is wake_time minus fall_asleep_minutes minus n times ninety. Each entry includes cycles, sleep_minutes (exactly n times ninety, not counting latency), and the zero-padded bedtime string. Latency is not added into sleep_minutes because it models time spent still awake after lights out; the bedtime is earlier so that true sleep can still fill whole cycles before the alarm.

Inputs, defaults, validation, and the response shape

The optional cycles parameter is an integer from one to twelve and defaults to six, covering about nine hours of pure sleep plus your fall-asleep buffer—enough range for most adult schedules without suggesting extreme twelve-hour nights unless you ask. The only required field is wake_time. It must be a string matching a strict twenty-four-hour pattern from 00:00 through 23:59; twelve-hour strings with AM or PM, bare numbers, and non-string values are rejected with invalid_input that names the field. The optional fall_asleep_minutes parameter is an integer from zero to one hundred twenty and defaults to fifteen, a common rule-of-thumb latency used in popular sleep-cycle charts. Values outside those ranges, non-integers, or a missing wake_time fail before any arithmetic runs, and those failures are not billed. On success the body echoes the normalized wake_time, the cycles and fall_asleep_minutes that were applied, cycle_minutes fixed at ninety, and the bedtimes array described above. Example: wake_time 07:00, cycles 5, fall_asleep_minutes 15 yields bedtimes 23:15 for five cycles (four hundred fifty minutes of sleep), then 00:45, 02:15, 03:45, and 05:15 for four through one cycles respectively. Pair the response with your own calendar UI if you want local timezone labels; this endpoint only reasons about wall-clock HH:MM values you provide.

Where a sleep cycle bedtime API earns its keep

School and shift-planning tools can precompute suggestions for fixed start times so users pick a sustainable lights-out clock rather than scrolling endlessly. Content sites that rank for sleep cycle bedtime calculator benefit from a free browser path that matches the paid automation path byte-for-byte on the same pure module, so demos and production jobs never disagree. Treat the ninety-minute cycle length as a practical planning heuristic, not a medical diagnosis; individual cycle lengths vary, and people with sleep disorders should follow clinical advice. Wellness apps and coaching bots need a tiny, offline-safe primitive that turns an alarm time into a short menu of bedtimes without shipping a sleep-science model or calling a cloud inference endpoint. API automation at $0.002 per successful call lets batch planners generate tables for many wake times—for example every fifteen minutes across a morning window—while invalid input never consumes balance.