Parsing Quarters via parse(input, qqq/yyyy, locale) results in April 1st for Q3 and Q4

[denmaddin]

I have an weired issue parsing quarter notations to an Date using the date-fns/parse()-Function.
Quarters notated in the pattern qqq/yyyy result in Q2/2020 (April 1st 2020) for the following Inputs:

• Q2/2020
• Q3/2020
• Q4/2020

Tested with Locale de and en as well as upper-case QQQ and lower-case qqq.
However using the pattern yyyy-qqq works as expected.

Versions tested: 2.9.0, 2.10.0
Versions affected: 2.9.0, 2.10.0

Side Note

After further analysis it seems that the first digit succeeding the Slash limits the resulting quarters.

• */1999 -> Q1, Q1, Q1, Q1
• */2000 -> Q1, Q2, Q2, Q2
• */3000 -> Q1, Q2, Q3, Q3
• */4000 -> Q1, Q2, Q3, Q4

qqq/yyyy Example

import parse from 'date-fns/parse';
import format from 'date-fns/format';
import { de, en } from 'date-fns/locale'

test() {
    const backupDate = new Date();
    const pattern = 'qqq/yyyy';
    
    const input1 = 'Q1/2020';
    const input2 = 'Q2/2020';
    const input3 = 'Q3/2020';
    const input4 = 'Q4/2020';
    
    const parsed1 = parse(input1, pattern, backupDate);
    const parsed2 = parse(input2, pattern, backupDate);
    const parsed3 = parse(input3, pattern, backupDate);
    const parsed4 = parse(input4, pattern, backupDate);
    
    const formatted1 = format(parsed1, pattern, {locale: de});
    const formatted2 = format(parsed2, pattern, {locale: de});
    const formatted3 = format(parsed3, pattern, {locale: de});
    const formatted4 = format(parsed4, pattern, {locale: de});
    
    console.log(`in: ${input1}; parsed: ${parsed1}; formatted: ${formatted1}`);
    console.log(`in: ${input2}; parsed: ${parsed2}; formatted: ${formatted2}`);
    console.log(`in: ${input3}; parsed: ${parsed3}; formatted: ${formatted3}`);
    console.log(`in: ${input4}; parsed: ${parsed4}; formatted: ${formatted4}`);
}

Output

in: Q1/2020; parsed: Wed Jan 01 2020 00:00:00 GMT+0100 (Mitteleuropäische Normalzeit); formatted: Q1/2020
in: Q2/2020; parsed: Wed Apr 01 2020 00:00:00 GMT+0200 (Mitteleuropäische Sommerzeit); formatted: Q2/2020
Q3/2020; parsed: Wed Apr 01 2020 00:00:00 GMT+0200 (Mitteleuropäische Sommerzeit); formatted: Q2/2020
Q4/2020; parsed: Wed Apr 01 2020 00:00:00 GMT+0200 (Mitteleuropäische Sommerzeit); formatted: Q2/2020

yyyy-qqq Example

import parse from 'date-fns/parse';
import format from 'date-fns/format';
import { de, en } from 'date-fns/locale'

test() {
    const backupDate = new Date();
    const pattern = 'yyyy-qqq';
    
    const input1 = '2020-Q1';
    const input2 = '2020-Q2';
    const input3 = '2020-Q3';
    const input4 = '2020-Q4';
    
    const parsed1 = parse(input1, pattern, backupDate);
    const parsed2 = parse(input2, pattern, backupDate);
    const parsed3 = parse(input3, pattern, backupDate);
    const parsed4 = parse(input4, pattern, backupDate);
    
    const formatted1 = format(parsed1, pattern, {locale: de});
    const formatted2 = format(parsed2, pattern, {locale: de});
    const formatted3 = format(parsed3, pattern, {locale: de});
    const formatted4 = format(parsed4, pattern, {locale: de});
    
    console.log(`in: ${input1}; parsed: ${parsed1}; formatted: ${formatted1}`);
    console.log(`in: ${input2}; parsed: ${parsed2}; formatted: ${formatted2}`);
    console.log(`in: ${input3}; parsed: ${parsed3}; formatted: ${formatted3}`);
    console.log(`in: ${input4}; parsed: ${parsed4}; formatted: ${formatted4}`);
}

Output

in: 2020-Q1; parsed: Wed Jan 01 2020 00:00:00 GMT+0100 (Mitteleuropäische Normalzeit); formatted: 2020-Q1
in: 2020-Q2; parsed: Wed Apr 01 2020 00:00:00 GMT+0200 (Mitteleuropäische Sommerzeit); formatted: 2020-Q2
in: 2020-Q3; parsed: Wed Jul 01 2020 00:00:00 GMT+0200 (Mitteleuropäische Sommerzeit); formatted: 2020-Q3
in: 2020-Q4; parsed: Thu Oct 01 2020 00:00:00 GMT+0200 (Mitteleuropäische Sommerzeit); formatted: 2020-Q4