$\text{1}$ It is ten days since I last saw Lan . 

→ The last time I saw Lan was ten days ago . 

→ I haven't seen Lan for ten days . 

$\text{2}$ It is a month since she last phoned me . 

→ The last time she phoned me was a month ago . 

→ She hasn't phoned me for a month . 

$\text{3}$ It is a year since they last ate fish . 

→ The last time they ate fish was a year ago . 

→ They haven't eaten fish for a year . 

$\text{4}$ It is eight months since it last rained . 

→ The last time it rained was eight months ago . 

→ It hasn't rained for eight months . 

$\text{5}$ It is six weeks since it last snowed .

→ The last time it snowed was six weeks ago . 

→ It hasn't snowed for six weeks . 

$\text{6}$ It is an hour since Tom last cried . 

→ Tom last cried an hour ago . 

→ Tom hasn't cried for an hour . 

$\text{7}$ It is three years since I last saw you . 

→ The last time I saw you was three years ago . 

→ I last saw you three years ago . 

$\text{8}$ It is a month since I last watched TV . 

→ The last time I watched TV was a month ago . 

→ I last watched Tv a month ago . 

$\Rightarrow$ The last time + S + Ved/cột 2 + was + time 

$\Rightarrow$ S + last + Ved/cột 2 + O 

$\Rightarrow$ It's + time + since + S + last + Ved/cột 2 + O 

$\Rightarrow$ S + hasn't/haven't + Vpp + O 

$\text{@Zyy}$