ICC events can have reserve days for knockout matches to ensure results. Not available in bilateral series.
Details
Reserve days are additional days allocated for ICC tournament matches that may be affected by weather:
World Cup/Champions Trophy: Semi-finals and finals typically have a reserve day. Group matches may or may not have reserve days.
WTC Final: Has a reserve day (6th day) if play is lost to weather during the scheduled 5 days.
T20 World Cup: Knockout matches have reserve days.
If a match cannot be completed even with the reserve day, the result is determined by: - In group stages: The match is abandoned (no result), and points are shared - In knockouts: Various tie-breaking methods apply (higher group position, NRR, etc.)
Bilateral series (tours) do not have reserve days — if a day's play is washed out, the overs are simply lost.
Historical Evolution
Reserve days have been used in ICC events for decades. The 2019 WC Final had no reserve day scheduled, which was criticized. The 2021 WTC Final had a reserve day that proved crucial as Day 1 was entirely washed out.
Current Rule
Reserve days allocated for ICC event knockout matches. WTC Final has a 6th day reserve. Group matches may not have reserve days.