When is my piversary?
Mathematica, 152 134 bytes

f[i_]:=DateList@{i,{d="Day",m="Month",y="Year"}}~DatePlus~{{3,#},{Round[#2*(Pi-3.)],d}}~DateString~{d,"/",m,"/",y}&amp;@@@{{m,31},{y,365}}


Ungolfed

f[i_] :=
 DateString[
    DatePlus[
     DateList@{i,{d="Day",m="Month",y="Year"}}, 
     {{3, #}, {Round[#2*(Pi - 3.)], d}}
    ],
    {d, "/", m, "/", y}
 ] &amp; @@@ {{m, 31}, {y, 365}}


This does handle leap years. It's also horribly long.