How to Save Time

This isn't a productivity talk. It's a survey of some idiosyncrasies related to persisting date/time values to a database.

Transcript

1. 

   How to Save Time
   Joel Clermont

   @jclermont
   

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2. Productivity
   

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3. ISO8601
   

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4. Date time values are tricky
   • Date math
   • Leap years/seconds
   • Daylight Saving Time
   • Time Zones
   • Many more . . .
   https://infiniteundo.com/post/25326999628/falsehoods-
   programmers-believe-about-time
   

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5. Approach 1
   Everything is local
   

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6. Everything is local
   2018-11-06T09:05:23
   

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7. Everything is local
   Pro: super easy, no thought/effort
   Con: What if you have users in a different time zone?
   

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8. Approach 2
   Local plus time zone offset
   

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9. Local plus offset
   2018-11-06T09:05:23-06:00
   

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10. Local plus offset
    Pro: can convert to other time zones
    Con: Not consistent, lots of tz values
    

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11. Approach 3
    Always store UTC
    

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12. Always store UTC
    2018-11-06T15:05:23Z
    2018-11-06T15:05:23+00:00
    

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13. Always store UTC
    Pro: able to convert, consistent
    Con: ?? Is there an unsolved problem?
    

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14. Problem
    Politicians can break your code
    

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16. What if the time zone
    rules change?
    

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17. https://www.timeanddate.com/news/time/
    

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18. https://www.timeanddate.com/news/time/
    

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19. Approach 4
    Future dates as wall time + tz name
    

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20. Future as wall + tz name
    2019-11-06T12:00:00
    America/Sao_Paulo
    

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21. Future as wall + tz name
    Pro: TZ rules can change
    Con: New time zones? God help you
    

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22. Questions?
    @jclermont
    

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23. Thank you!
    @jclermont

    

    

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