def sec2HMS(sec):
    """Convert time in sec to H:M:S string
    
    :param sec: time in seconds
    :return: H:M:S string (to nearest 100th second)
    
    """
    H = int(sec // 3600)
    M = int(sec // 60 - H * 60)
    S = sec - 3600 * H - 60 * M
    return '%d:%2d:%.2f' % (H, M, S)
