# DaysLeft

> DaysLeft is a free, privacy-first web app that estimates your **biological age** and **how fast you're aging** (speed of aging) — either from your daily habits (2-minute quiz) or from nine standard blood-test markers (PhenoAge). It is a mirror for behavior change, not a medical diagnosis or a life-expectancy prediction.

Key facts (citable):
- Two modes: a 2-minute lifestyle quiz, and a precise mode using 9 routine blood markers via the validated PhenoAge model (Levine et al., 2018; 10-year mortality AUC ≈ 0.88).
- Country-aware life tables (e.g., US CDC NVSR, with regional fallbacks) drive the remaining-time distribution.
- Results are shown as a distribution and confidence band — never a single "you will die at X" point estimate.
- Privacy: calculation inputs are computed on your device. Biological-age, blood values, and mental-health screening data are never sent to a server. Anonymous usage analytics may be collected for product metrics unless turned off; they do not include sensitive inputs. No signup, no account.
- Safety: 18+ only; a PHQ-2 depression screen routes at-risk users to support (988 / findahelpline.com) instead of showing mortality content.
- Free to use.

## Core pages
- [Biological age test (2-min quiz)](https://daysleft.io/calc): estimate biological age and speed of aging from habits — smoking, exercise, diet, sleep.
- [PhenoAge calculator (blood-based)](https://daysleft.io/precise): validated biological age from 9 checkup blood markers, computed on-device.
- [Speed-of-aging simulator](https://daysleft.io/simulate): see how changing one habit shifts your biological age and remaining time.

## Guides
- [Biological age test — what it is](https://daysleft.io/en/guide/biological-age-test)
- [How fast are you aging?](https://daysleft.io/en/guide/how-fast-are-you-aging)
- [Biological age calculator explained](https://daysleft.io/en/guide/biological-age-calculator)
- [How to lower your biological age](https://daysleft.io/en/guide/how-to-lower-biological-age)
- [Biological vs chronological age](https://daysleft.io/en/guide/biological-age-vs-chronological-age)
- [Free longevity test](https://daysleft.io/en/guide/free-longevity-test)
- [PhenoAge calculator](https://daysleft.io/en/guide/phenoage-calculator)

## About
- [Privacy](https://daysleft.io/privacy): on-device computation for sensitive inputs; anonymous usage analytics may be collected unless turned off.
- [Terms](https://daysleft.io/terms): not a medical device; a statistical estimate and self-awareness tool.