"If I let them come in between 8 and 10, do I still have to record the exact time for each one?". The HR manager of an accounting firm with 22 administrative employees asked me this, convinced that flexible hours freed her from keeping timesheets. The answer made her uncomfortable: flexibility changes how you record the workday, not if you record it. Here I explain how flexible hours and reliable recording coexist in an Argentine office, what the regulations say, and how to configure windows without ending up chasing people for five minutes.