df =

ID   TYPE  DATETIME
1    A     12/18/2015 23:02:00
1    A     12/17/2015 12:00:09
1    A     12/18/2015 18:04:08
2    B     12/20/2015 15:03:05
2    B     12/18/2015 14:02:07

ID   TYPE  DATETIME
1    A     12/17/2015 12:00:09
1    A     12/18/2015 18:04:08
1    A     12/18/2015 23:02:00
2    B     12/18/2015 14:02:07
2    B     12/20/2015 15:03:05

df.groupby("ID").sort(...)