Report Setup Disable Clause

Hi, I am trying to setup a report with the following parameters:

1. Performance Date
2. Season
3. Entrance Doors
4. Time of Day
5. Previous Year Season

I need to disable the Previous Year Season parameter if the Performance Date is before 02/21/2017. I tried entering a disable clause of <<p1>> < '02/21/2017' but it is not functioning properly. When I go into Tessitura Client and try to run the report, the parameter is not disabled for any date. Can anyone please advise on how to fix this issue?