In service industries personnel performance is key to achieve business excellence. Until recently, forty to forty eight hours per week labor contracts with equal daily schedules (eight hours per day) was the only way formal employees were hired in some countries. Recently, this trend has changed and some countries started to allow work contracts with less weekly hours and flexible daily schedules. This offers some degrees of freedom to employees to work less than eight hours per day and non-necessarily having the same timetable every workday. The fabric of society is impacted since now work is at reach for many people who cannot work full time schedules for diverse reasons. The contribution of this work is a Transdisciplinary Flextime Hiring Method that considers both employee and company needs. Using organisational design concepts (business management), flexibility is analysed through integer programming modelling (engineering optimisation) to evaluate cost changes resulting from implementing flextime (societal needs). Service companies may justify and implement flextime based on cost reductions, along with its associated improvement of employee satisfaction and commitment. Numerical analysis based on industry data illustrates these concepts and consequences.