In the Dates tab of the urban Model Settings window, your simulation start and end times are specified.
For Kinematic Wave or Dynamic Wave routing, a time and date should be defined to Start Analysis on. It is common to Start Reporting on the same date and time. Ensure you End Analysis on a date and time such that your simulation accounts for the storm event. Recall if you have defined absolute dates/times in any timeseries data associated to Urban Inflow, these should be taken into consideration here.
For a Steady urban simulation, the Start Analysis on time/date will be used, but as this is the time-invariant case, the end date is irrelevant.