Workflow Automation trigger based on past/older date?

Workflow Automation trigger based on past/older date?

Is it possible to trigger a workflow automation based on a date value that occurred in the past?  

Here's the scenario:  Twice a month we have an admin enter leads manually, which are collected from an offline lead source. The "transaction" dates from these leads will be anywhere from two days to two weeks old.  

We want to perform follow-ups 30 and 90 days after this (past) transaction date.  I set up a rule to trigger on a date value, and set that value to the transaction date, which is typically 2 to 14 days older than today's date. The rule doesn't seem to trigger with the older date. 

Any ideas?