Invalid dates are parsed as valid

Invalid dates are parsed resulting in incorrect values e.g, const dt = dayjs(‘1993-51-11’) dt.isValid() returns true and dt.format('YYYY-MM-DD') returns 1997-03-11 const dt = dayjs(‘1993-51-41’) dt.isValid() returns true and dt.format('YYYY-MM-DD') returns 1997-04-10 infact dayjs('1993-08-21', 'YYYY/MM/DD') returns true for isValid()

isValid() should return false for all these

Information

• Day.js Version: v1.9.6
• OS: macOS 11 BigSur
• Browser: chrome 86
• Time zone: GMT

[iamkun]

Do remember this dependent on CustomParseFormat plugin to work https://day.js.org/docs/en/parse/string-format

[rrdlpl]

For the people that still are struggling with this. As the other people mentioned you need CustomParseFormat

const dayjs = require("dayjs")
require('dayjs/locale/en')
const customParseFormat = require('dayjs/plugin/customParseFormat');
dayjs.extend(customParseFormat);

const datestr= '20201312'

console.log(dayjs(datestr, 'YYYYMMDD', 'en', true).isValid());