chronos.ai

About the Project ChronosAI is a CP-SAT-first scheduling assistant. You describe your plans in plain English; the LLM only parses your intent into a strict schema, and a deterministic OR-Tools CP-SAT model does all time math, feasibility, and optimization. The result is explainable, safe scheduling with hard guarantees like “no overlaps” and “before the deadline.” What inspired us Most “AI calendars” let a model pick times directly, which is brittle for time zones, buffers, and conflicts. We flipped the pattern: • LLM: parsing only (extract structure, never schedule). • CP-SAT: constraint satisfaction + optimization (do the hard math deterministically). This split keeps the system reliable, auditable, and predictable. What we learned

How we built it

Schema the LLM must output (per item): { "intent": "event|meeting|task", "title": "string", "start_dt": "ISO8601 or null", "deadline_dt": "ISO8601 or null", "availability_windows": [{"start":"ISO","end":"ISO"}], "duration_minutes": 30, "can_split": true, "confidence": { "overall": 0.0, "start_dt": 0.0, "deadline_dt": 0.0, "availability": 0.0, "duration_minutes": 0.0 }, "assumptions": ["notes the LLM inferred"] } The scheduling math (at a glance) We discretize time into slots (e.g., 15 minutes). For each item i with duration D_i (in slots) and feasible windows W_i, we build candidate starts [ \mathcal{S}i={\,t \mid [t,t+D_i)\subseteq W_i\,}. \] Meetings/events choose exactly one start: [ \sum{t\in\mathcal{S}i} x{i,t}=1. \] Tasks may split across blocks subject to min/max session lengths and daily caps. We enforce NoOverlap across all chosen intervals (existing busy + buffers + new placements). Our objective (weighted sum) typically minimizes: [ \alpha \cdot \text{lateness} +\beta \cdot \text{fragmentation} +\gamma \cdot \text{energy_penalty} +\delta \cdot \text{churn}. \] Spaced repetition appears as a dispersion preference and per-day caps so blocks don’t cluster and never overlap. Challenges we faced What we’re proud of Tech notes With this architecture, ChronosAI stays friendly and conversational while still delivering hard scheduling guarantees.