it's
((略式))1 it is [has] の短縮形2 〔誤用〕＝its
It's a date.
その日時［時間］でいいよ，それで決まりだね（◆会う約束の日時の都合を確認して）“How about Friday [tomorrow night]?” “It's a date.”「金曜日［明日...
It's a free country.
((米略式))ここは自由の国だよ；（相手に対して）どうぞご自由に；（自分の行為について）私の勝手だろ
It's a good thing [((英))job] (that) ....
（…であって）運がよかった
It's a safe [good, sure] bet that ....
((略式))…はまず間違いなさそうだ（It seems almost certain that ...）
