what is the location of 在

正 is used to describe where something is happening or existing, and can also be used to describe a specific time frame.

1) 在 + Verb/Adjective or Subject
他在到了巴黎以后才直到这个消息。 (He did not know the news until he had arrived in Paris.)
飞机在下午三点半到达。(The plane arrived at 3:30 p.m.)
在当时，这个问题还不严重。(At the time, the problem was not serious.)

2) Verb + 在
会议时间定在后天上午。(The meeting is scheduled for the morning after tomorrow.)
故事发生在很久以前。(The story happened a long time ago.)

3) Verb + 在 or 在 + Verb
他出生在上海。(He was born in Shanghai.)
他在上海出生。(He was born in Shanghai.)

"在" is a versatile and important word in Chinese that can be used in a variety of ways to express location, action, or state.
To indicate location, the sentence structure usually is:
- Subject + "在" + Place
or
- Subject + "在" + Place +action verb.