Making a gantt type chart in excel using if statements

So I basically have to create a gantt type chart that automatically fills in the start and end month of the project. The problem I'm having is that I have a specific start and end date like, Start: 06/17/18 and End: 07/20/19. My Chart is categorized by months and not specific dates, so for this example I would need it to populate the cells starting from June 2018 until July of 2019. I'm having some problems because I made an if statement that looked at the month and populated the cells by month, however, it would then only fill in the june and july cells of 2018 and 2019 and would leave all the other cells in between blank. I then added another filter for it to also look at the year, except it didn't help because since my "if statement" looks for everything in between the 6th and 7th month, it doesn't populate the 8th, 9th and other months of the rest of 2018 and the beginning months of 2019.

Here is my if statement: =IF(AND(MONTH(N$3)>=MONTH($I5),MONTH(N$3)<=MONTH($J5), YEAR(N$3)>=YEAR($I5),YEAR(N$3)<=YEAR($J5)),"")