If we want to trigger an email when it has been X days since a subscriber last made a purchase, we create a filter with the rule Order.date, in this case 120 days ago. In the filter, you can of course choose how many days you want.

1. Click on "Subscribers"
2. Then on "Segments"

   
   

Then on "+ New segment" in the upper right corner

1. Name the segment
2. Choose the tag "OrderCompleted"
3. Check "Regular segment"
4. Create

Then you will see this view, and then you should set up the rule for your segment

1. Make sure "All" is filled in
2. In the first field, choose "OrderDate", in the next field "exact number of days since" and lastly choose the number of days, in this case 120
3. Save and sync

After the segment is created, go back to "Journey Builder", double check that the trigger is correct, just like in the step above. Then change the segment to the one you created.