Even the most clear cut, fixed laytime regimes agreed in a voyage charter can still give rise to disagreement – whether it be about when a vessel became an arrived ship, whether a particular load rate was achieved, or whether or not an interruption has been properly credited in a laytime calculation. However, this is made infinitely more complicated where parties agree to a laytime regime by reference to, for example, weather working days. The definition in English law of what constitutes a weather working day is straightforward: it is a day on which the weather permits the relevant work to be done. Whether any cargo operations are carried out is irrelevant; as long as the weather does not prevent those operations from taking place, laytime counts. The essential issue is therefore the character of the day (i.e. whether or not any adverse weather was experienced) and not whether work was actually interfered with ( Reardon Smith [1963] 1 LLR 12, at p41 ). This extends also to any periods after the vessel has become an arrived ship but before having berthed. In other words, if the prevailing weather conditions would have permitted the vessel to be worked, had she been in berth, laytime counts. Conversely, any periods during which adverse weather would have prevented working of the vessel in berth are excluded from the laytime calculation. Where matters become a bit more complicated and contentious is in relation to: (a) what constitutes weather for the purpose of interrupting laytime; and (b) evidence of those weather conditions. What constitutes weather for the purpose of interrupting laytime Largely, this is a factual question and is dictated by the type of vessel and the type of cargo being carried. For example, for a dry bulk vessel carrying sugar in bulk, rain would constitute bad weather but for a crude oil tanker, it would not. In addition, the weather must be adverse to cargo operations and not some other operation. The usual type of adverse weather experienced