<story><title>Storing UTC is not a silver bullet (2019)</title><url>https://codeblog.jonskeet.uk/2019/03/27/storing-utc-is-not-a-silver-bullet/</url></story><parent_chain><item><author>samwillis</author><text>I think summary here is that if you are storing an exact moment in time then UTC does the job. If however you are storing a future date and time in a certain location, due to the uncertainty about future daylight saving time changes you have to save it with time zone information in order to adjust for future changes to that system.&lt;p&gt;I suppose it’s the difference between exact time and social&amp;#x2F;political time (there is probably a better term for that).</text></item></parent_chain><comment><author>alecbz</author><text>Yeah, this is exactly the difference between what I’d call “timestamps” (something that represents a particular instant in time), and what I’d call “datetimes”, things like “midnight on Jan 1, 2019”.&lt;p&gt;I worked at an insurance startup that stored coverage period start&amp;#x2F;ends as timestamps, which ended up being semantically wrong. The coverage ends at midnight of the next year, wherever _you_ (technically the provider, I think) are. So there is no one single instant in time when coverage ends; a timestamp is the wrong data type for representing this.</text></comment>
<story><title>Storing UTC is not a silver bullet (2019)</title><url>https://codeblog.jonskeet.uk/2019/03/27/storing-utc-is-not-a-silver-bullet/</url></story><parent_chain><item><author>samwillis</author><text>I think summary here is that if you are storing an exact moment in time then UTC does the job. If however you are storing a future date and time in a certain location, due to the uncertainty about future daylight saving time changes you have to save it with time zone information in order to adjust for future changes to that system.&lt;p&gt;I suppose it’s the difference between exact time and social&amp;#x2F;political time (there is probably a better term for that).</text></item></parent_chain><comment><author>masklinn</author><text>&amp;gt; due to the uncertainty about future daylight saving time changes&lt;p&gt;It’s not just DST, it’s any TZ-related changes: locations can change TZ for other reasons than dst.&lt;p&gt;&amp;gt; I suppose it’s the difference between exact time and social&amp;#x2F;political time.&lt;p&gt;There’s really no such thing as exact time. The closest is UT1, and it’s not really practical for normal applications.</text></comment>