What is the cutoff period in your organization to be eligible for appraisal?

I joined the company in september, its been six months. But the company is saying that you need to complete atleast 9 months to be eligible for appraisals. The cycle happens once in a year. If I miss this cycle, then I need to wait for atleast 18 months since I joined for getting a raise. I joined this company on same package while making a switch, because I was desparate to get a job in my hometown.

I want to understand what is the cutoff in your organization? Can I negotiate for exception?