The number of days is calculated by subtracting the Elective care waiting list episode-listing date for care from the Hospital census (of elective surgery waitlist patients)-census date, minus any days when the patient was 'not ready for surgery', and also minus any days the patient was waiting with a less urgent clinical urgency category than their clinical urgency category at the census date.

Days when the patient was not ready for surgery is calculated by subtracting the date(s) the person was recorded as 'not ready for surgery' from the date(s) the person was subsequently recorded as again being 'ready for surgery'.

If, at any time since being added to the waiting list for the elective surgical procedure, the patient has had a less urgent clinical urgency category than the category at the census date, then the number of days waited at the less urgent Elective surgery waiting list episode-clinical urgency, code N category should be subtracted from the total number of days waited.

In cases where there has been only one category reassignment (i.e. to the more urgent category attached to the patient at census date) the number of days at the less urgent clinical urgency category should be calculated by subtracting the Elective care waiting list episode-listing date for care from the Elective care waiting list episode-category reassignment date. If the patient's clinical urgency was reclassified more than once, days spent in each period of less urgent clinical urgency than the one applying at the census date should be calculated by subtracting one Elective care waiting list episode-category reassignment date from the subsequent Elective care waiting list episode-category reassignment date,  and then adding the days together.

When a patient is admitted from an elective surgery waiting list but the surgery is cancelled and the patient remains on or is placed back on the waiting list within the same hospital, the time waited on the list should continue. 

Therefore at the census date the patient's waiting time includes the number of days waited on an elective surgery waiting list, both before and after any cancelled surgery admission. The time waited before the cancelled surgery should be counted as part of the total time waited by the patient.