Data Sources and Quality

MarketClock never invents a fact. Everything comes from the library or from an exchange or regulator page that was opened and read, stored with its URL. If a fact cannot be verified, it is left out and the app says "not on file".

Data	Source
Closures and half days	the holidays library (never copied, cached in Redis)
Weekend days	the library's market class
Name, country, timezone	exchange websites, with source URL
Session hours, early-close times	exchange websites, with source URL (NYSE, Nasdaq, JPX, HKEX, ASX, LSE so far)
Settlement cycles	exchange or regulator notices, with effective date (US, Canada, UK so far)
Official calendars, for checking	exchange calendars, with the date they were checked

Data quality

The official_closure table holds whole years of an exchange's published calendar. The /data-quality page and endpoint compare them day by day with the library and list any day missing, extra, or with a different kind (closed or half day). NYSE (2026 to 2028), Nasdaq (2026) and LSE (2027 and 2028) match exactly. A real difference is reported upstream to the holidays library, so every user benefits.

Not on file yet

Session hours for TSX, Tadawul, NSE and SGX; settlement cycles for PSX, BSE and NSE; official calendars for PSX and Tadawul. Their sites were down or denied access when checked. If you can point to an official page, open an issue with the link.

Details: docs/architecture.md.