In the NEC3, 'day' refers to an individual day as opposed to a working day, both when calculating :
- any change to the contractual Completion Date (under clause 63.3 in ECC); and
- delay damages. So when an Employer is setting the level of damages, they need to take this into account to avoid them be construed as punitive i.e. a penalty, which are generally not allowed except, as I understand, in the USA and Arab countries. E.g. calculate the damages per week of delay and divide by 7 days, not 5.
Under JCT, a day includes weekends but excludes bank holidays. So if the architect said "you have seven days to do 'X'" and there was a bank holiday, then the Contractor would in fact have eight.