Bat Timeline DCNU
Batman The Dark Knight #0
This issue details Bruce right after his parents death and roughly up to the point that he leaves Gotham. It focuses on Bruce tracking down Joe Chill up to his early college years.
10 Years Ago
Detective Comics #0
The opening of the issue states this book begins 10 years ago. Bruce's training in the Himalayas is featured here and it also mentions his training and travels to other locations.
The back up story begins seven years ago. It's in this story that we see Bruce's return to Gotham and he is reunited with Alfred.
6 Years Ago
This story begins 6 years ago. Bruce is in the early stages of his crime fighting career and has not donned the cowl yet. His main feud here is with the Red Hood gang and his early outings don't end well. In the issue James Gordon states that Bruce Wayne returned to Gotham 3 months ago. Therefore, he's been training and stockpiling his weapons cache here for nearly a year (9 months of it under the general public's radar). It should also be noted he is NOT operating out of the Batcave here, instead operating out of a Brownstone near Crime Alley.
The back up story takes place 5 years ago. It focuses on Dick, Jason, Tim and Barbara. It sheds more light on Dick Grayson's timeline in becoming Robin. In this back up, he mentions he is performing for Bruce Wayne the following weekend which is when his parents are killed. Also, Tim Drake states he is in middle school
making him roughly 12-14 years old assuming he is between the 6th and 8th school grades. Therefore Bruce becomes Batman between 5 and 6 years ago.
5 Years Ago
Justice League #1
Of course, this is the first encounter between Batman and Green Lantern. He later allies himself with GL, Flash, Cyborg, Wonder Woman, Superman and Aquaman against Darkseid.
Five years ago we see Dick Grayson's origin and ascension to becoming the first Robin. His origin is retold here and in his first outing he assists Bruce against Lady Shiva.
4 Years Ago
Four years ago, we see Barbara's evolution into Batgirl. During an altercation at the GCPD she dons a makeshift Bat suit and helps apprehend a criminal. She begins her career as Batgirl afterwards and operates under the identity for one year before giving it up to focus on her college studies. It is at this point in time she is shot by the Joker.
Red Hood & The Outlaws #0
The retelling of Jason Todd's story. This obviously takes place after Nightwing's #0 issue.
Teen Titans #0
Tim Drake's origin, it deviates a good deal from his original story. Bruce and Alfred refer to Jason's death as being very recent in this one. An exact time table isn't listed.
18 Months Ago
Batman & Robin #0:
Bruce and Damian meet for the first time. From this date we know that Damian has been Robin for less than 18 months.