How to present pre-era dates as a UNIX timestamp

Question

It occurred to me that I did not know the mechanism for storing dates until 1970. 1 as Unix timestamps. Since this date is the Unix era, this is not a big surprise.

But, even if it is not intended for this, I still want to store dates in the distant past in Unix format. I need this for reasons.

So my question is: how could one make unix-timestamps contain "invalid" but still working dates? Will a negative number of seconds be saved? Can we even store negative seconds in unix-timestamp? I mean, isn't he unsigned?

Also, if I am right, then I could keep the dates back to 1901. dec. 13 20:45:52 1901. dec. 13 20:45:52 , if it were perhaps even more continued in history by any means?

Answer 1

Unix Time is usually a 32-bit integer second since the first moment of 1970 in UTC, epoch 1 January 1970 00:00:00 UTC . This means that about 136 years and a half on both sides of the era. Negative numbers are earlier, zero is an era, and positive ones are later. For a signed 32-bit integer, the values ​​range from 1901-12-13 to 2038-01-19 03:14:07 UTC .

It is not written in stone. Well, it is written, but in a bunch of different stones. Older ones talk about 32-bit, newer 64-bit. Some specifications are that the meaning is “implementation-defined”. Some Unix systems use unsigned ints to propagate only into the future for the era, but common practice has been a signed number. Some use a float rather than an integer. See the Wikipedia article on Unix Time and this question for more details.

So basically, your question does not make sense. You need to know the context of your programming language (standard C, another C, Java, etc.), the environment (POSIX-compatible), a specific software library or database storage or application.

Avoid the countdown from the era

Add to this the lack of specificity of the fact that a couple of dozen other eras were used by various software systems, some of which are extremely popular and widespread. Examples include January 1, 1601 for the NTFS and COBOL file systems, January 1, 1980 for various FAT file systems, January 1, 2001 for Apple Cocoa, and January 0, 1900 for Excel and Lotus 1-2-3 spreadsheets.

Next, add the fact that different counting granularities were used. In addition to whole seconds, some systems use milliseconds, microseconds, or nanoseconds.

I recommend from date-time tracking as an account-from-era. Instead, use the specific data types available in your programming language or database. When they are not available or when exchanging data, follow the ISO 8601 standard , which defines reasonable string formats for different date and time values.

• the date
  • 2015-07-29
• Date-time offset from UTC (Z - “Zulu” for UTC) (note filling zero at offset)
  • 2015-07-29T14:59:08Z
  • 2001-02-13T12:34:56.123+05:30
• Week (with or without a day)
  • 2015-W31
  • 2015-W31-3
• Order term (day)
  • 2015-210
• Interval
  • "2007-03-01T13:00:00Z/2008-05-11T15:30:00Z"
• Duration ( PnYnMnDTnHnMnS format)
  • P3Y6M4DT12H30M5S = "three years, six months, four days, twelve hours, thirty minutes and five seconds"

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