(a) Except as provided by chapter 71 of title 41, every civil
action commenced against the United States shall be barred unless
the complaint is filed within six years after the right of action
first accrues. The action of any person under legal disability or
beyond the seas at the time the claim accrues may be commenced
within three years after the disability ceases.
(b) A tort claim against the United States shall be forever
barred unless it is presented in writing to the appropriate Federal
agency within two years after such claim accrues or unless action
is begun within six months after the date of mailing, by certified
or registered mail, of notice of final denial of the claim by the
agency to which it was presented.