The actual text of the Constitution is the final and absolute yardstick all laws are measured against. When the Supreme Court considers the constitutionality of any law it must measure the law against the original text of the constitution and its plain meaning when it was written.
Notice of working hours/changes. Your employer must give you reasonable notice of any changes to your working hours, such as cancelling your shifts. They may request last minute changes (such as ringing you that morning to say that they do not require you to work) and you can choose to agree to this change.
Rounding Hours Worked. Some employers track employee hours worked in 15 minute increments, and the FLSA allows an employer to round employee time to the nearest quarter hour. However, an employer may violate the FLSA minimum wage and overtime pay requirements if the employer always rounds down. Employee time from 1 to 7 minutes may be rounded down, and thus not counted as hours worked, but employee time from 8 to 14 minutes must be rounded up and counted as a quarter hour of work time.