Answer
$\Delta T=1h$
Work Step by Step
$T=2\pi\sqrt{\frac{l}{g}}$
$\frac{\Delta l}{l}=$
$\frac{\Delta T}{T}=\sqrt{\frac{\Delta l}{l}}=\sqrt{(19\times10^{-6})(12^oC)}=0.0151s$
$t=5.52s$
$\frac{T-T_i}{T_i}=\frac{2\pi\sqrt{\frac{l}{g}}-2\pi\sqrt{\frac{l_i}{g}}}{2\pi\sqrt{\frac{l_i}{g}}}$
$\frac{\sqrt{l}-\sqrt{l_i}}{\sqrt{l_i}}=\frac{\sqrt{l_i+\alpha l_i\Delta T}-\sqrt{l_i}}{\sqrt{l_i}}=\sqrt{1+\alpha\Delta T}-1=\sqrt{1+(19\times10^{-6})(12)}-1=1.14\times10^{-4}$
$T_i=365\frac{days}{year}\frac{24hours}{1day}\frac{60min}{1hour}\frac{1min}{60s}=3.154\times10^7s$
$\Delta T=(3.154\times10^7s)(1.14\times10^{-4})=3600s=1 h$
