Sessions & Challenges

A market session is the window during which Market Owners publish challenges and Forecasters submit forecasts for them.

Session lifecycle

A new market session opens every hour, on the hour; its gate closure is the top of the next hour (HH:00).

Within each session, the Market Owner publishes one or more challenges, each with a specific forecast window. See Challenge horizons below for the authoritative reference on challenge types and their forecast windows.

A session proceeds in four phases:

1. Session opens — for one hour.
2. Challenges are published — creating opportunities for you to submit forecasts to.
3. Forecasters submit — pull raw data, build models, POST forecasts before gate closure.
4. Session closes — no more submissions accepted. Next session opens.

Tip

See the sequence diagram for a visual walk-through.

Within each session, Market Owners can publish multiple challenges with different forecast windows. For example, a session might include a 24-hour-ahead (intraday) forecast challenge and a day-ahead (D+1) forecast challenge, each with its own submission requirements and reward rules. Forecasters can choose which challenges to participate in based on their expertise and resources.

To maximize your chances of earning rewards, consider submitting to multiple challenges within the same session, if you have the capacity to do so. Using our API, you can automate the process of fetching challenge details and submitting forecasts to multiple challenges efficiently.

Challenge horizons

Predico publishes forecasting challenges across three horizon categories — how far ahead the target period sits relative to the session that spawned the challenge. The category governs the evaluation window and the prize envelope.

For scoring, rankings and prize amounts, see Evaluation & Prizes — the single source of truth for prize information.

Horizons and publishing schedule

Sessions open every hour on the hour (CET) and their gate closure is the top of the following hour (HH:00 CET). Which categories are published depends on the gate-closure hour:

Category	Target window	Published at (gate closure, CET)
Intraday	The 24 h immediately after gate closure.	Every hour
Day-Ahead (D+1)	The next calendar day (00:00 → 24:00 local).	10:00
Extended (D+N)	A day 2–10 days ahead (D+2, D+3, …, up to D+10).	10:00

On a typical weekday you therefore get 24 intraday opportunities per resource, plus "extended" waves covering day-ahead and the longer horizons.

gate_closure is authoritative

Always read the gate_closure field returned by the API for the specific session/challenge you are targeting — do not hard-code the hours above.

How to tell which category a challenge is in

Every challenge carries start_datetime / end_datetime (anchored to Belgian local time, CET/CEST) plus a human-readable horizon label in its metadata — no need to parse internal field names.

Time and timezones

• REST API responses use UTC for all datetimes, independently of the target resource's local time. Always convert to the target resource's local time zone before interpreting the challenge's forecast window.
• Challenges forecast periods (i.e., timestamps to forecast) are anchored to the target resource's local time (typically CET/CEST for Belgian assets).
• Time resolution can vary per resource and is driven by the Market Owner's requirements. Trust the challenge metadata (start_datetime, end_datetime, and the expected number of values) over any assumed cadence.

Daylight Saving Time

On DST-transition days a challenge may cover more or fewer than 24 hours:

• March (CET → CEST): 23 values — local hour 02:00–03:00 is skipped.
• October (CEST → CET): 25 values — local hour 02:00–03:00 repeats.

The challenge's start_datetime / end_datetime always spell out the exact expected coverage.