Amazon Prime Day Sees Its Biggest Year Yet According to the software company Feedvisor, Prime Day started at 9 p.m. ET in 2017 and lasted for 30 hours. This year, it started at 3 p.m. ET on Monday and lasted 36 hours. The number of orders also increased 22% this year in the same period of time as last year. Amazon representative in email, via CNN The success of the event didn’t seem to be affected by the periodic outages on the site shortly after it kicked off. "Sad news: Amazon seems to be crashing from demand for Prime Day sales…" Overall, retail think tank Coresight Research predicts