def dt_dt(sdat, tstart=None, tend=None):
    """Derivative of temperature.

    Compute dT/dt as a function of time using an explicit Euler scheme.

    Args:
        sdat (:class:`~stagpy.stagyydata.StagyyData`): a StagyyData instance.
        tstart (float): time at which the computation should start. Use the
            beginning of the time series data if set to None.
        tend (float): time at which the computation should end. Use the
            end of the time series data if set to None.
    Returns:
        tuple of :class:`numpy.array`: derivative of temperature and time
        arrays.
    """
    tseries = sdat.tseries_between(tstart, tend)
    time = tseries['t'].values
    temp = tseries['Tmean'].values
    dtdt = (temp[1:] - temp[:-1]) / (time[1:] - time[:-1])
    return dtdt, time[:-1]