Use since for a specific point in time.

对于特定的时间点使用 since。

Since relates to a specific point in time so we use it with dates.

Since 涉及到一个特定的时间点，所以我们用它来表示某个日期。

Now, you need to use " since" with a specific moment in the past - with a specific point in time.

用单词 " since" 你需要加过去的一个特定时间，一个特定的时间点。

Here we're talking about a specific point in time.

在这里，我们谈论的是一个特定的时间点。

When molten rock cools, its magnetic minerals are " frozen" at a specific point in time.

当熔岩冷却时，其磁性矿物会在特定时间点“冻结”。

Now there's also some really common fixed expressions that use the preposition " at" when you're referring to a specific point in time.

那么还有一些非常常见的固定的表达方式，会用到介词 " at" ，在你指某个特定的时间点的时候。

Later on in the week, later on in the year. Okay, so it's not a specific point in time but it's just in the future at some point.

本周晚些时候，今年晚些时候。好的，并不是特定的一个时间，只是未来的某个时间。

So " at the end of" or " at the start of" a period of time is also a common way to refer to a specific point in time.

那么" at the end of" 或 " at the start of" 是一段时间，同样是一种指特殊时间点常见的方式。

" It is to give ... confidence, at a specific point in time, that the result is positive or negative, " said Christian Paulus, a Roche research and development manager.

罗氏制药的研发经历克里斯蒂安·保卢斯表示：“它是在特定时间点给大家信心，结果是阳性或是阴性。”

At tells us that this is a really specific moment, a specific point in time and using by suggests that the report should be finished at any point up until that point in time.

At 表明这是一个具体的时刻，一个具体的时间点，by 则表明报告应该在该时间点之前任何一个时间完成。