It's time to punch the timeclock and head out because it's beer o'clock. Here's a record of the earliest known such time. It's a cuniform tablet that is 5,000 years old.
Archaeologists found it at Uruk (you know, from Star Trek) in modern-day Iraq. It illustrates laborers being paid for their services in the best form of currency: beer. Alison George describes at New Scientist:
On one tablet excavated from the area we can see a human head eating from a bowl, meaning “ration”, and a conical vessel, meaning “beer”. Scattered around are scratches recording the amount of beer for a particular worker. It’s the world’s oldest known payslip, implying that the concept of worker and employer was familiar five millennia ago.