When claims are denied, the denial notice will advise you that you have 60 days to appeal. On your initial application, you have 17 months from the start of your disability to file a claim without losing past-due benefits. This is not a formal deadline but the failure to make a timely filing can be costly. When in doubt as to filing an initial claim, you are entitled to request a "protective filing" which will preserve past-due benefits. The protective filing is valid for 6 months.
We always recommend that you consult with an experienced attorney before contacting SSA for your disability claim.