fix(priceforecast): bucket local hours, not UTC - #1166
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Hour-of-week and month indexing used t.UTC(), so the baked Nordic evening peak (17–20 local) landed 1–2 hours late in CET/CEST. Fit and Predict now share the Europe/Stockholm civil clock. Closes #1161 Signed-off-by: Fredrik Ahlgren <fredrik@sourceful-labs.com>
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| // The baked prior is a Nordic local-hour shape; UTC indexing put CEST | ||
| // evening peaks two hours late (19:00 CEST = 17:00 UTC). Stockholm is | ||
| // CET/CEST, matching SE1–SE4 / DK / NO / DE. | ||
| var bucketTZ = mustLoadTZ("Europe/Stockholm") |
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When cfg.Price.Zone is outside CET/CEST, this global Stockholm clock misaligns the baked prior with that market's civil hours. For example, a fresh or sparsely trained PT model treats 16:00 Portuguese winter time as Stockholm 17:00 and therefore starts the evening peak an hour early; Finland and the Baltic zones are shifted in the opposite direction. These are supported price zones, main.go passes the configured zone directly to NewService, and the forecast is wired into the MPC, so the bucket location should be derived from ZoneModel.Zone rather than fixed to Stockholm.
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Accepted text proposal
Issue or Discussion: #1161
Maintainer comment that accepted this scope: issue #1161.
What changed
Price-forecast hour-of-week and month buckets now use the Europe/Stockholm civil clock (CET/CEST) instead of UTC. Fit and Predict share that conversion, so the same instant still maps to the same bucket regardless of the
time.Timelocation.The baked Nordic prior is a local-hour shape (morning 07–09, evening 17–20). UTC indexing put CEST evening peaks two hours late: 19:00 CEST is 17:00 UTC.
Package comments no longer claim that Predict downweights by MAE/counts; those fields remain diagnostics.
go/internal/prices/prices.gois untouched (#1044 and #1051).Why
Overnight fill after the day-ahead cutoff used the wrong diurnal shape for Nordic sites. A SE3 19:00 CEST peak must land in the evening prior bucket, not the UTC-17 bucket.
Boundaries and safety
Out of scope: harvest/tariff in
prices, MPC VAT blend, using MAE/counts as a confidence weight. Missing tzdata cannot silently fall back to UTC — the package embedstime/tzdata.Verification
cd go && go test ./internal/priceforecast -count=1 -timeout 60sChecklist
Closes #1161
Note
Medium Risk
Changes how forecasted spot prices are shaped for MPC horizons beyond day-ahead; wrong timing directly affected Nordic arbitrage planning, but the change corrects intentional local-hour semantics rather than introducing new behavior.
Overview
Fixes #1161 by indexing price-forecast hour-of-week and month buckets on the Europe/Stockholm civil clock instead of UTC, so fit and predict both align with the baked Nordic prior (evening 17–20 local). Under UTC, a 19:00 CEST peak was bucketed like 17:00, shifting evening shape 1–2 hours late for overnight MPC fill before day-ahead prices land.
The package embeds
time/tzdataso stripped hosts and tests do not silently fall back to UTC. Package docs now describe Counts/MAE as refit diagnostics rather than MPC confidence weights. Tests use Stockholm local times and add a regression that 19:00 CEST maps to the Wednesday 19 bucket and beats 21:00 local.Reviewed by Cursor Bugbot for commit 344ea12. Bugbot is set up for automated code reviews on this repo. Configure here.