What is Unix Timestamp (Epoch)?
Unix Timestamp expresses the total number of seconds that have passed since January 1, 1970, 00:00:00 UTC (Coordinated Universal Time). This date is called the "Unix Epoch". Since it is not affected by time zones, it is the most reliable method for transferring date data between computer systems.
Why 1970?
In the years when the Unix operating system was developed (1969-1971), 1970 was chosen as a suitable starting point (epoch) for 32-bit systems. Although it seems like a random choice, it is one of the milestones of computer history.
The Year 2038 Problem (Y2K38)
32-bit signed integer systems can store a maximum of 2,147,483,647 seconds. This counter will fill up on January 19, 2038, and systems may fail, returning the date to 1901 or 1970. This problem has been solved in modern 64-bit systems (they can work smoothly for 292 billion years).