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.
Working time. Working time is the period of time that a person spends at paid labor. Unpaid labor such as personal housework or caring for children or pets is not considered part of the working week. Many countries regulate the work week by law, such as stipulating minimum daily rest periods, annual holidays, and a maximum number of working hours per week.