After seeing Suicide Squad again, I was not happy with the discrepancy that Joker and Harley Quinn killed Robin, while earlier this year Zack Snyder said that Jason Todd was killed in 2005, when Harley would have only been 15 or 16. That makes no sense.
Here's what I think it should have been:
1995: Bruce becomes Batman, in my head he had a similar origin to Batman: Year One.
1998: After being Batman for three years, Bruce adopts Dick Grayson (age 14) as Robin after his family is killed (like in Dark Victory)
2003: Dick Grayson (age 19) becomes Nightwing; leaves for Bludhaven. Bruce adopts Jason Todd as the second Robin later that year.
2005: Joker kills Jason Todd, is sent to Arkham Asylum after Batman beats his teeth out.
Sometime in the early 2010's: Joker is treated by Harleen Quinzel in Arkham, then manipulates and transforms her into Harley Quinn.