Cooper said he would probably change his shopping hours if he knew what times certain products were on special.
Brett Ashley, general manager of operations for Countdown, said his supermarkets tried to offer customers specials throughout the week but there were a few tricks savvy shoppers could use to save money.
"Look out for markdowns," he said. "Markdowns are the most common way our supermarkets ensure there is minimal waste of products which are nearing their best-before or expiry dates.
"Our store and department managers are constantly on the lookout for any products where freshness may be compromised. Often this means products which perish more quickly are marked down early in the morning. Shoppers may notice more markdowns on things like meat, yoghurt and packaged salads at this time."
Ashby said bakery items, like fresh bread and pastries, were often discounted mid-afternoon to make space for the next day's fresh bakery items.
Come in a little later, after 6pm perhaps, and shoppers might find items like hot chickens marked down to encourage sales.
Countdown also usually ran specials in the lead-up to the weekend, Ashby said. "The end of the week is a great time to shop for these huge specials and we'll usually have some additional specials on fruit and veges at this time, too."
Rob Chemaly, general manager of retail for Foodstuffs Auckland, said New World and Pak'nSave were committed to providing customers with a great-value shopping basket regardless of the day of the week or time they choose to shop.
"We do not believe in forcing consumers to go out of their way to visit a supermarket at inconvenient times in order to get the best deals possible."
But calls revealed that individual supermarkets got their orders in at certain times in the week: the seafood counter at Pak'nSave Royal Oak gets tuna on Wednesday or Thursday, which may be discounted by the weekend. And sliced bread, baked in-store, is discounted from late afternoon every day.
Similarly, the New World supermarket in Freemans Bay gets its big produce delivery on Thursday; some fruit and veges such as limes, chillies, tamarillos and capsicums may run out by the middle of the following week.
At that supermarket, North Shore teacher Jessica Macartney said she was aware there were good times to shop but she couldn't change the time of her grocery trips because of her working hours. "I used to do it in Australia but I don't do it here because it's not so pronounced."
Janee Schupp, a mother of three young children, said she wasn't aware of time-dependent specials but it didn't make much difference.
"I'd still go when I need to because with three children I need to pick my moments when it works to go shopping."