Fare Calendar

Project intro

Fare Calendar answers the question travel agents ask on every phone call — 'which day is cheapest?' — before they run a full search. It is a drop-in web component that shows the lowest fare under every date: a dot marks a real fare an agent actually got in the last 3 days ('seen'), and a dotted underline marks a model estimate with a likely range for dates nobody searched recently. It is built entirely from the booking portal's own server logs, so it reflects the fares that portal's suppliers actually return, not a public metasearch. Supplier response formats (GDS SOAP XML, Navitaire XML, IATA NDC XML and JSON) are handled by a small mapping language; Gemma 4, running locally, wrote 7 of the 11 supplier mappings, each validated by code against real responses before use, with the rest hand-written and labelled as such. Unsearched dates are filled by Chronos-Bolt forecasts averaged with a same-weekday baseline, with gaps passed as gaps rather than invented. On the author's production logs (one month, 11,544 searched dates across 14 backtest cutoffs), the calendar covers 41% of the dates agents go on to search (up from 36% with seen fares alone), with 1.0% error on recent real fares and 16.2% error on estimated dates, versus 18.7% for the weekday baseline alone. Everything is labelled indicative and agents reprice live before booking. Note on demoUrl: the author's public Render demo (fare-calendar-demo.onrender.com, synthetic data) was re-checked live by the publisher before publishing, so demoUrl points to the running demo. The production deployment itself is behind a sign-in page and is not public.