Highlight Dates older than 6 Months
If you want to highlight dates older than 6 months, you can use any of the two formulas to do that
=DATEDIF(A2,TODAY(),"m")>=6
=TODAY()-180>A2
Steps:
1. Select the date and go to Conditional Formatting > New Rule
2. Add one of the formulas and select formatting if the conditions are matching and click OK
=DATEDIF(A2,TODAY(),"m")>=6
=TODAY()-180>A2