"ID"      "date"      "d_days" "group"
"00377698" 2006-11-15 -1006   "pre"
"00377698" 2009-08-16 -1      "pre"
"00377698" 2009-08-17 0       "ref"
"00377698" 2009-08-24 7      "post"
"00377698" 2009-09-03 17     "post"
"00377698" 2009-10-09 53     "post"
"00377698" 2010-02-26 193    "post"
"00377698" 2010-08-27 375    "post"
"00377698" 2010-11-26 466    "post"
"00377698" 2011-08-24 737    "post"
"00540688" 2009-06-26 -1664  "pre"
"00540688" 2009-08-20 -1609  "pre"
"00540688" 2009-11-20 -1517  "pre"
"00540688" 2010-11-17 -1155  "pre"
"00540688" 2011-12-07 -770   "pre"
"00540688" 2014-01-09 -6     "pre"
"00540688" 2014-01-15 0      "ref"
"00540688" 2014-01-20 5      "post"
"00540688" 2014-03-05 49     "post"
"00540688" 2015-04-29 469    "post"
"00540688" 2015-09-30 623    "post"
"00540688" 2016-05-13 849    "post"

"ID"      "date"      "d_days" "group"
"00377698" 2006-11-15 -1006   "pre"
"00377698" 2009-08-17 0       "ref"
"00377698" 2011-08-24 737    "post"
"00540688" 2011-12-07 -770   "pre"
"00540688" 2014-01-15 0      "ref"
"00540688" 2015-09-30 894    "post"