A Caution about Unix Time

In the beginning

• Unix measures time in the number of seconds since January 1, 1970
• This was an arbitrary date picked during the development of Unix, which was during the late 60's and early 70's.
• the Unix time() function returns an int, which on most machines is a 32 bit value
• ... with the first (leftmost) bit=0 for positive numbers and 1 for negative numbers

Things to come

• At GMT 03:14:07 on Tuesday, January 19, 2038 it will have been 2,147,483,647 seconds since Unix began counting.
• this is ... 2**31-1
• and the Unix time value will roll over
  • from 01111111111111111111111111111111
  • to     10000000000000000000000000000000
  • to     10000000000000000000000000000001
• Which equals -1
• What will happend as we move through this singularity?
• Some say this will be
  • 20:45:52, Friday, December 13, 1901, or maybe
  • December 32, 1969

What lies beyond

• Should you fly on 1/19/2038?
• It's not recommended.
• Stay at home and guard it from the roving bands of starving retirees seeking food that began to appear after the Social Security checks stopped coming in 2035.