12点15用英语表达是：a quarter past twelve；

quarter：n. 四等份之一; (正点之前或之后的)15分钟，一刻钟; 三个月时间; 季度; 季。

past：adj. 过去的; 昔日的; 刚过去的; 刚结束的; 从前的; 以往的。

相关介绍

We should have finished by a quarter past two and the bus doesn't leave till half past.

两点一刻时我们应该就完成了，而公共汽车要到两点半才开。

It is a quarter past eight by my watch, but it may be a little fast.

我的表是8点1刻，可能快了一点。

It's quarter to four now ─ I'll meet you at quarter past.

现在是差一刻四点，我会在四点一刻和你碰面。

It's a quarter past four. it's tea time.

现在4点15分了，是用茶点的时间了。

He gets back home at a quarter past five.

他到家是在五点一刻。