gistfile1.txt

0) Iterate over each branch
1) Iterate over the list of commits in your branch that aren't in master
2) If it has multiple parents, skip it
3) Get the date of the commit
4) Perform date magic
...
???) Profit

# Gets commits unique the branch, not in master
git rev-list topicbranch ^master 

# Get the parents of a particular commit hash, space separated
git log --format=format:"%%P" --max-count=1 commithash

# Get the date of a particular hash
git log --format=format:"%%cD" --max-count=1 commithash