Flex-time policies are fairly common among U.S. employers, and allow employees to arrive and leave work within a defined time range, instead of having to arrive and leave at a precise start and end time. As a cautionary tale, in McMillan v. City of New York, such a flex time policy precluded the employer from holding the employee accountable for tardiness. The employee, Rodney McMillan, had schizophrenia, but his mental disability was controlled with medication. Despite his disability, he worked successfully for ten years as a case manager for the City of New York. The City's flex time policy allowed employees to arrive at work anytime between 9:00 and 10:00 a.m. Employees were considered late if they arrived after 10:15. McMillan often arrived late to work, sometimes after 11:00 a.m. He attributed his tardiness to drowsiness caused by his schizophrenia medication. For ten years, the City tolerated his tardiness.

However, a new manager began to hold McMillan accountable for arriving on time. The City commenced a disciplinary process for McMillan's continued tardiness. As a result, McMillan formally requested accommodation for his disability, including a later flex start time that would permit him to arrive at work between 10:00 and 11:00 a.m. The City rejected the request as unreasonable, and placed McMillan on 30-day suspension without pay for repeated tardiness.

McMillan sued for violation of the federal ADA. In defense, the City urged that arriving at work by 10:15 was an essential function of the job and that McMillan was not a qualified worker covered by the ADA because of his history of tardiness. The federal district court agreed and dismissed the suit.

On appeal, the federal Second Circuit Court of Appeals remanded the case for a jury trial, holding that although courts will normally give considerable deference to an employer's determination that arrival at work at a particular time is an essential requirement, "the fact that the City's flex-time policy permits all employees to arrive and leave within one-hour windows implies that punctuality and presence at precise times may not be essential." Further, in this case, McMillan's late arrivals were tolerated for a decade before the City decided to take disciplinary action. Accordingly, the court ruled that a jury must decide whether arriving at a specific time was an essential function of the job, and whether McMillan's request for a later start time was reasonable or an undue hardship. Employers with companywide flex-time policies should evaluate whether to exclude positions that require punctuality and presence at work at precise times.