I was afraid that the business days was like referring to McDonald jones business in which case the business days wouldn't start up again till today!!!
There is a clause in the HIA building contract that allows for a Christmas shutdown period which lasts a few weeks(I think), but I thought they would still need to give you notice 20 days prior if they will use that? Not sure. At the very least, take off all the public holidays and get rid of the weekends then count 20 days..
Anyway, we were on the construction list 12/12/13 and the site was pegged (That is considered commencement) on the 17/01/14
Cheers,
Brad