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Parsing dates with negative year in Go?

How do I parse the date "3 Mar -1500" to represent 1500 BC?

https://play.golang.org/p/akqQPj4mLeo

1 Answer
1

Here is a first draft that illustrates the concept:

package main

import (
"fmt"
"strings"
"time"
)

func parseCEDate(value string) (time.Time, error) {
const layout = "_2 Jan 2006"
date, err := time.Parse(layout, value)
if err == nil {
return date, err
}
perr, ok := err.(*time.ParseError)
if !ok {
return time.Time{}, err
}
if perr.LayoutElem != "2006" {
return time.Time{}, err
}
if !strings.HasPrefix(perr.ValueElem, "-") {
return time.Time{}, err
}
value = strings.Replace(value, perr.ValueElem, perr.ValueElem[1:], 1)
date, derr := time.Parse(layout, value)
if derr != nil {
return time.Time{}, err
}
return date.AddDate(-2*date.Year(), 0, 0), derr
}

func main() {
fmt.Println(parseCEDate("3 Mar -1500"))
fmt.Println(parseCEDate("3 Mar 1500"))
}


Playground: https://play.golang.org/p/QtZ5BBSJmHJ

Output:

-1500-03-03 00:00:00 +0000 UTC <nil>
1500-03-03 00:00:00 +0000 UTC <nil>


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