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While chrono supports parsing of date, time and time zone in ISO 8601 compliant format, I am unable to find any method in the crate to parse duration strings such as PT2M which represents 2 minutes.

Shepmaster
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praveent
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3 Answers3

4

Chrono doesn't have any function to do this job.

Instead, use the parse_duration crate to solve the problem:

extern crate parse_duration;
use parse_duration::parse;

fn main() {
    print!("{:?}", parse("2 minutes"));
}

Ok(120s)

Furthermore, there isn't any function that converts ISO 8601 shortcuts into a representation for the chrono or parse_duration crate.

You need to write a parser that transforms the shortcuts like PT2M into a human readable form like 2 minutes, if you work with the parse_duration crate.

If you want to use the chrono crate directly, you have a lot of calculation to do to put the duration into a numeric representation. I would take a look into the sources of parse in parse_duration.

One workaround could be to calculate the duration out of two NaiveDates:

extern crate chrono;
use chrono::{Duration, NaiveDate};

fn main() {
    let d = NaiveDate::from_ymd(2021, 8, 2);
    let tm1 = d.and_hms(0, 0, 0);
    let tm2 = d.and_hms(0, 2, 0);
    let delta: Duration = tm2.signed_duration_since(tm1);
    print!("{:?}", delta);
}

Duration { secs: 120, nanos: 0 }
Kaplan
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    I'm surprised at this result. I wouldn't have thought that `".:++++]][][[][[2]][minutes][]:}}}}"` was a valid duration. – Shepmaster Aug 02 '21 at 14:48
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    I guess the OP knows how [ISO 8601](https://www.digi.com/resources/documentation/digidocs/90001437-13/reference/r_iso_8601_duration_format.htm) works. Why would he ask otherwise explicit for a function to parse this format? – Kaplan Aug 02 '21 at 15:03
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    @Kaplan thanks for reference. Unfortunately, package has no longer updating notice. The reason I referenced chrono is that it is nearly feature complete with parsing ISO8601 duration. I would have very much liked to limit my dependencies. – praveent Aug 02 '21 at 15:49
  • I added a workaround that reduces the time-calculations, that are needed to instantiate a `Duration` directly. Nevertheless You must still write a parser which transforms the ISO 8601 eg. `PTM2` into `(0, 2, 0)` for 2 minutes. – Kaplan Aug 02 '21 at 16:37
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    @Shepmaster The workaround is an addendum in response to the OP's [latest comment](https://stackoverflow.com/posts/comments/121278717?noredirect=1) *limit my dependencies* and not a new solution. – Kaplan Aug 02 '21 at 17:39
  • @Kaplan sure... but why are you telling me this? – Shepmaster Aug 02 '21 at 17:41
  • @Shepmaster Due to a *don't reply twice* comment, which has disappeared in the meantime. Sorry, I thought it came from you. – Kaplan Aug 02 '21 at 18:07
2

Chrono doesn't have any function to do this job.

You can use iso8601-duration crate instead.

Pascal Pixel Rigaux
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1

There is also the iso8601 crate which can parse durations and dates in that format.

Lukas Kalbertodt
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