R,Y,G status help

[Fed Firefighter]

New to the forum and need some help. I am inputting data at work and am stumbling creating a red, yellow, green status for a due date. I am in charge of tracking equipment testing on cylinders firefighters wear to fires. The cylinders need to be tested every 5 years. I have all of the data input into the spread sheet and am fumbling from here. The due date (listed as month and year) example due May-2019. I am trying to make a red status if cylinder is within a year of testing or past the due date, in this case May-2018 to May-2019. Yellow status for two years from the due date May-2017 to May-2018. Lastly, Green three years from the date May-2014 to May-2017. A tricky part is cylinders have different due dates, not everyone is the same. I am sure that this has been answered 1,000 times. I tried searching and am unsure of the words to use.

Thanks in advance,

Ken


Attached is my spread sheet. The column I am referring to is Column E "Hydro Due".