period={p1:{R:{M:'-1'}},p2:{R:{D:{start:'-28',end:'-1'}}

RE_DAY_END = re.compile(r'(D:{start:'-d+',end:')+(?P<dend>-[0-9]+)')
match_day= RE_DAY_END.findall(x)
print(match_day)

I am not interested:  [("D:{start:'-28',end:'", '-1')]

  I need this one:      [("D:{start:'-28',end:'-1')]