A claim under this subpart may be allowed only if it is filed in writing within 2 years after accrual of the claim. For the purpose of this part, a claim accrues at the later of:

1. (a) The time of the accident or incident causing the loss or damage;
2. (b) Such time as the loss or damage should have been discovered by the claimant by the exercise of due diligence; or
3. (c) Such time as cause preventing filing no longer exists or as war or armed conflict ends, whichever is earlier, if a claim otherwise accrues during war or an armed conflict or has accrued within 2 years before war or an armed conflict begins, and for cause shown.