It's also non-extensible so these types it's missing cannot be added without assumptions or overhead from convention.
Transit is a good solution to this.
1. ISO UTC 2. ISO local 3. Epoch 4. 2018-04-20 5. Jan 01 2016 11:58am
Probably others that I can't recall. It's a damn mess.
That will probably cause a twitch to any dev that used Asp.NET up until a few years ago.
I never understood why simple integer unix timestamps are not more prevalent in API-s? Or some monotonic count from any reasonable epoch, depending on the context. How many APIs really have to ever return dates predating unix?
Current precision with a 32-bit float (JSON/JavaScript are 64-bit usually, though in non-JS it's common to use Bigdecimal in slight non-compliance) is much worse than one second.
That's the point, timestamps should be self-describing. If "look up the structure in documentation" suffices we might as well just use protobufs.
I dunno, how do you distinguish "April" (the month) vs "April" (someone's first name) or 18 (kg) vs 18 ($) vs 18 (-th of the month) vs 18 (page number)?
> It is lower fidelity (seconds vs milliseconds).
This isn't a problem if you have a conforming implementation (2^52 milliseconds is over 100'000 years), but as nitrogen pointed out, you do apparently have to worry about that.
This is a frequent gotcha with Typescript, where even if your type is declared with a Date field, Javascript won't care when it deserializes it, as that type information is all erased and not available at runtime.
(Also, Number in JS being floating point and all, it lacks the integer precision for high resolution timestamps - if you start serialising 64 bit timestamps and expect a JS-style runtime to do good things with them it doesn't end well.)
Ah, thanks, that makes sense; I'd forgotten that Javascript had a built-in Date type. (Strictly speaking, then, you ought to be able to write something like `{"time":new Date(...)}`, but that obviously doesn't work in practice.)
Types! Extensible types. Like I said above, Transit is a good solution to this. With a fixed set of types, arbitrary data will always have ambiguity.
You alarm will be an hour off when you convert to UTC beforehand.
A timestamp is a point in time, whatever the time is in Paris or Tokyo. It is an abstract value and it is way better this way.
A timezone is a filter through which you display your timestamp, and it tells you what your local time was when that timestamp occurred.
So yeah, always store and exchange time information as timestamps. Timezone is extra styling information, just like CSS.
> Timezone is extra styling information, just like CSS.
This is an incredibly reductive view of time data and the possible applications that use it.
Not all time data is timestamps, and UTC timestamps strip out information that is not "styling".
You might not have encountered such scenarios but they are very much out there.
Expressing time based on the standard reference timezones (i.e., UTC) is not stripping the time zone away.
Example: The EU will most likely get rid of DST around 2022. Any time you set beforehand in CEST or CET will be an hour off, depending on which the EU will get rid of.aybe the EU doesn't get rid of DST and keeps it, you don't know. So unless you have a time machine, you cannot convert the time to UTC.
There are lots of examples like this. Some time events you want to happen at absolute time points (in which case time zones are only for display purposes), but very often your events need to be ”time-zone aware”. There is no universal rule, and thinking that there is will lead to all sorts of trouble.
A timestamp is a point in time, and is the same everywhere (excluding relativistic effects).
What you describe is definitely a valid use case (and having developed software that programs hardware that is controlled by a calendar, I have painful experience in this). However, it's not a timestamp. I'd call it time-of-day or wallclock. Some systems like SQL refers to it as simply "date" and "time". Whatever you prefer to call it, it's not a timestamp.
How you represent it doesn't change the definition. It could be stored as the number of seconds since some arbitrary point in time, such as Unix timestamp, or a Julian timestamp.
Or, it could be a given time and date combination with some fixed point of reference, such as UTC. I'm sure we all have favourite ways of representing timestamps.
When I set an alarm for any time in CEST in 2022 and convert this to UTC before saving it, it will very likely ring at the wrong time, simply because CEST will probably not exist by then and be replaced by CET due to the EU getting rid of DST.
Dates should not be encoded with time zone info anyway, as timezones is context-dependent. Dates should be encoded in UTC and then let clients interpret them according to their context.
Maybe OP meant timestamp, but that's not what they wrote.