Sleep Cycle Calculator

from datetime import datetime, timedelta

SLEEP_CYCLE_MINUTES = 90
FALL_ASLEEP_MINUTES = 14  # Average time to fall asleep

def wake_times_from_bedtime(bedtime: datetime, cycles: int = 5) -> list[datetime]:
    """Given a bedtime, return optimal wake-up times after N full 90-min cycles."""
    fall_asleep = bedtime + timedelta(minutes=FALL_ASLEEP_MINUTES)
    return [
        fall_asleep + timedelta(minutes=SLEEP_CYCLE_MINUTES * i)
        for i in range(1, cycles + 1)
    ]

def bedtimes_from_wake(wake_time: datetime, cycles: int = 5) -> list[datetime]:
    """Given a desired wake time, return bedtimes that allow N full 90-min cycles."""
    return [
        wake_time - timedelta(minutes=SLEEP_CYCLE_MINUTES * i + FALL_ASLEEP_MINUTES)
        for i in range(1, cycles + 1)
    ]

# Example: bedtime at 11 PM
bedtime = datetime.now().replace(hour=23, minute=0, second=0, microsecond=0)
print(f"Bedtime: {bedtime.strftime('%I:%M %p')}")
print("Best wake times:")
for t in wake_times_from_bedtime(bedtime):
    print(f"  {t.strftime('%I:%M %p')} ({(t - bedtime).seconds // 60} min)")

# Example: must wake at 7 AM
wake = datetime.now().replace(hour=7, minute=0, second=0, microsecond=0)
print(f"\nWake time: {wake.strftime('%I:%M %p')}")
print("Best bedtimes:")
for t in bedtimes_from_wake(wake):
    print(f"  {t.strftime('%I:%M %p')}")