Conditional Format - Dates greater than 18 months and 24 months

Here's my problem:

I have a date column (Column E: Date Entered) on my spreadsheet that I need to set conditional formatting on. There are two conditions:

1) 18 months from the date in the cell needs to be highlighted yellow
2) 24 months from the date in the cell needs to be highlighted red

It seemed simple enough when I started but I'm having trouble figuring this one out. Any advice would be much appreciated.

Thank you,
Amanda