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Creative Deletion
creativedeletion.com · Personal blog · on HN since 2009
Creative Deletion is a developer's blog on time zones, datetimes, and the Elixir language.
What HN saysHN commenters recommend its "Falsehoods programmers believe about time zones" list as a reading before handling dates, though one finds it depressing and wants fuller explanations.
18HN people shared it
9linked it in comments
22stories submitted
503story points
2 years agolast shared
2009people per year2026
Most-shared posts
- 1Falsehoods programmers believe about time and time zones10 people · 139 points · first shared 2015 · 80 comments on HN
- 2How to save datetimes for future events7 people · 93 points · first shared 2015 · 95 comments on HN
- 3Elixir – The next big language for the web2 people · 162 points · first shared 2015 · 82 comments on HN
- 4The need for timezone awareness1 people · 52 points · first shared 2015 · 60 comments on HN
- 5Timezone updates need to be fixed1 people · 36 points · first shared 2015 · 58 comments on HN
- 6Using Elixir instead of cron1 people · 9 points · first shared 2018 · discussion on HN
- 7Is Elixir getting more popular in the last year?1 people · 4 points · first shared 2019 · discussion on HN
- 8Data types and assumptions and how incorrect assumptions made a spacecraft crash1 people · 2 points · first shared 2019 · discussion on HN
- 9World time is more than GMT offsets1 people · 2 points · first shared 2009 · discussion on HN
- 10Why not to ask the server for its “local time”1 people · 2 points · first shared 2015 · discussion on HN
- 11How more time types prevent bugs and add clarity1 people · 1 points · first shared 2016 · discussion on HN
- 12Adding a function to the Elixir standard library that I hope will not be used1 people · 1 points · first shared 2019 · discussion on HN
- 13Wifi in sydney available but sparse expensive restricted1 people · first shared 2009
What HN people wrote when they linked it
JdeBP · 2019-03-06
The "S" stands for "Summer", and I strongly recommend reading things like https://infiniteundo.com/post/25509354022/more-falsehoods-programmers-… and http://creativedeletion.com/2015/01/28/falsehoods-programmers-date-tim… before confidently making statements on this subject.
thih9 · 2025-01-15
It’s difficult to maintain basic features in a popular calendar, at least according to the ms exchange team blog:
> calendaring is particularly tricky. Why’s that? Well, consider time zones for a start – a meeting you set up isn’t necessarily in the same time as it is for me, and then you also invited people, from a whole bunch of other time zones (did you know some time zones are 30 mins off, not a full hour?) (…)
https://techcommunity.microsoft.com/blog/exchange/calendaring-is-reall…
Then there is the “falsehoods programmers believe about time” list: https://gist.github.com/timvisee/fcda9bbdff88d45cc9061606b4b923ca , with some counter examples: http://www.creativedeletion.com/2015/01/28/falsehoods-programmers-date…
svieira · 2021-04-03
If you're writing a calendar app, then you should probably store the triple of `local time`, `time zone name`, `version of time zone database used to look up time zone name`
https://codeblog.jonskeet.uk/2019/03/27/storing-utc-is-not-a-silver-bu…
and
http://www.creativedeletion.com/2015/03/19/persisting_future_datetimes…
ArtDev · 2020-09-08
This is kinda depressing reading for the start of the workweek.
Also, I wish each of these was more expanded.. I can think of many workarounds for each of these situations but I am curious what other people's solutions might be:
http://www.creativedeletion.com/2015/01/28/falsehoods-programmers-date…
1-more · 2020-07-09
There is a case to not store a time in UTC: you schedule a meeting in the future and the local authorities change when they start DST in that location. Now your user gets the alert an hour too early or late for their meeting. The scenario is more fleshed out in the link below but I don't want to just copy and paste the article into the comment.
http://www.creativedeletion.com/2015/03/19/persisting_future_datetimes…
bradknowles · 2020-01-30
Anytime someone starts talking about creating a solution to the time zone problem, I will invite them to ensure they’ve at least thought about the problems raised at:
https://infiniteundo.com/post/25326999628/falsehoods-programmers-belie…
http://www.creativedeletion.com/2015/01/28/falsehoods-programmers-date…
https://puzzling.org/technology/computer-programming/2012/06/more-fals…
And so on.
beckler · 2019-06-18
I don't think anyone is saying that you shouldn't store datetimes in UTC. It's just that time is complex and the errors can be subtle, and you don't want to mess up appointments across timezones because you didn't factor in the timezone when appointment was originally made.
http://www.creativedeletion.com/2015/03/19/persisting_future_datetimes…
coldtea · 2016-08-26
>Time is actually quite simple if you have a good mental model of what you're trying to represent and don't try to mix different concepts into a single value.
Not even close.
http://www.creativedeletion.com/2015/01/28/falsehoods-programmers-date…
laut · 2016-04-18
UTC can also fail if your users need to see or enter times that are not in UTC. E.g. for a meeting or a train schedule or an appointment etc. See this http://www.creativedeletion.com/2015/03/19/persisting_future_datetimes…