Question 1

What is Unix timestamp?

Accepted Answer

A Unix timestamp (or Unix epoch) is the number of seconds that have elapsed since January 1, 1970, at 00:00:00 UTC. It is a simple and universal way to represent a moment in time as a single integer, used widely in programming, databases, and APIs.

Question 2

What is ISO 8601 format?

Accepted Answer

ISO 8601 is an international standard for representing date and time. The common format is YYYY-MM-DDTHH:MM:SS, for example 2024-01-15T14:30:00. The T separates the date and time portions. This format is unambiguous and sortable, making it ideal for data interchange.

Question 3

What is the difference between 12-hour and 24-hour time?

Accepted Answer

12-hour format divides the day into two 12-hour periods: AM (midnight to noon) and PM (noon to midnight), using hours 1-12. 24-hour format (military time) uses hours 0-23 without AM/PM, making it unambiguous. For example, 2:30 PM is 14:30 in 24-hour format.

Question 4

How do I convert 12:00 AM vs 12:00 PM?

Accepted Answer

12:00 PM is noon (midday), and 12:00 AM is midnight. This is one of the most confusing aspects of 12-hour time. In 24-hour format, noon is 12:00 and midnight is 00:00 (or 24:00 to indicate end of day).

Question 5

What is UTC and how does it relate to timestamps?

Accepted Answer

UTC (Coordinated Universal Time) is the primary time standard by which the world regulates clocks and time. Unix timestamps are always in UTC — they represent seconds since 1970-01-01 00:00:00 UTC. When displaying local time, you apply a timezone offset to the UTC timestamp.

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