def find_cal_indices(epoch_time):
    """
    Cal events are any time a standard is injected and being quantified by the system. Here, they're separated as though
    any calibration data that's more than 10s away from the previous cal data is a new event.

    :param epoch_time: array of epoch times for all of the supplied data
    :return: list of cal events indices, where each index is the beginning of a new cal event
    """
    epoch_diff = epoch_time.diff()
    indices = [i - 1 for i in epoch_diff.loc[epoch_diff > 10].index.values.tolist()]  # subtract one from all indices
    return indices