It's a Go module for parsing ISO 8601 durations and converting them to the often much more useful time.Duration.

ISO 8601 is a pretty common standard and sometimes these durations show up in the wild.

go get github.com/sosodev/duration

package main
import (
	"fmt"
	"time"
	"github.com/sosodev/duration"
)
func main() {
	d, err := duration.Parse("P3Y6M4DT12H30M5.5S")
	if err != nil {
		panic(err)
	}
	
	fmt.Println(d.Years) // 3
	fmt.Println(d.Months) // 6
	fmt.Println(d.Days) // 4
	fmt.Println(d.Hours) // 12
	fmt.Println(d.Minutes) // 30
	fmt.Println(d.Seconds) // 5.5
	
	d, err = duration.Parse("PT33.3S")
	if err != nil {
		panic(err)
	}
	
	fmt.Println(d.ToTimeDuration() == time.Second*33+time.Millisecond*300) // true
}

This module aims to implement the ISO 8601 duration specification correctly. It properly supports fractional units and has unit tests that assert the correctness of it's parsing and conversion to a time.Duration.

With that said durations with months or years specified will be converted to time.Duration with a little fuzziness. Since I couldn't find a standard value, and they obviously vary, for those I used 2.628e+15 nanoseconds for a month and 3.154e+16 nanoseconds for a year.