I have a dataset that looks like this:

State City Year Name 1990Q1 1990Q2 1990Q3 1990Q4
A B C D 1 2 3 4
E F G H 5 5 5 5


Etc.

I'd like to change this into a dataset that looks like:

State City Year Name Timeperiod Sales
A B C D 1990Q1 1
A B C D 1990Q2 2
A B C D 1990Q3 3
A B C D 1990Q4 4
E F G H 1990Q1 5
E F G H 1990Q2 5
E F G H 1990Q3 5
E F G H 1990Q4 5

How in the world do I automate this?