Issues

• locale() normalizes case/hyphen fallback but not underscore separators (zh_TW, pt_BR, etc. silently fail)

  iamkun/dayjs#3345 · Filter by author rusackas opened on Oct 29, 2026

• add()/subtract()/diff() silently treat 'isoWeek' as milliseconds when the isoWeek plugin is loaded

  iamkun/dayjs#3286 · Filter by author rahul05ranjan opened on Oct 24, 2026
  1

• fix localized format for cs locale

  iamkun/dayjs#3282 · Filter by author Iaotle opened on Oct 19, 2026

• duration plugin: leading sign of an ISO 8601 duration is ignored ("-P1D" parses as +1 day)

  iamkun/dayjs#3279 · Filter by author philppplik opened on Oct 19, 2026
  1

• Built locale/ku.js exports a wrapper object, not the locale

  iamkun/dayjs#3271 · Filter by author akamfoad opened on Oct 14, 2026

• [Regression in 1.11.22] Instance .tz() breaks when Intl.DateTimeFormat.prototype.formatToParts is missing or unreliable

  iamkun/dayjs#3270 · Filter by author QuentinRoadstr opened on Oct 14, 2026

• Calendar callbacks ignore an explicit referenceTime

  iamkun/dayjs#3246 · Filter by author kazuki-netizen opened on Oct 5, 2026

• customParseFormat: week token ('w'/'ww') is silently ignored when parsing with dayjs.utc()

  iamkun/dayjs#3239 · Filter by author AliGaffarToksoy opened on Sep 27, 2026

• objectSupport manipulation methods throw on nullish arguments

  iamkun/dayjs#3236 · Filter by author xu91102 opened on Sep 26, 2026

• Day predicates fail with different instance and global numeral locales

  iamkun/dayjs#3234 · Filter by author xu91102 opened on Sep 26, 2026

• relativeTime treats a zero threshold as an unlimited bound

  iamkun/dayjs#3232 · Filter by author xu91102 opened on Sep 26, 2026

• devHelper incorrectly warns that diff(0) has an invalid comparison date

  iamkun/dayjs#3230 · Filter by author xu91102 opened on Sep 26, 2026
  2

• Saved localeData objects mix languages after changing the global locale

  iamkun/dayjs#3228 · Filter by author xu91102 opened on Sep 26, 2026

• Vulnerabilities in transitive dependencies of dayjs (karma, semver, rollup, moment)

  iamkun/dayjs#3225 · Filter by author deepbytelab opened on Sep 21, 2026

• tz.guess() returns deprecated IANA alias "Asia/Calcutta" instead of canonical "Asia/Kolkata"

  iamkun/dayjs#3194 · Filter by author jasminbhesaniyajb opened on Aug 31, 2026

• TypeScript errors occur when using isSameOrBefore and isSameOrAfter

  iamkun/dayjs#3192 · Filter by author patienry opened on Aug 28, 2026

• diff(..., 'year'|'month', true) returns 0 instead of NaN for an Invalid Date operand

  iamkun/dayjs#3186 · Filter by author yfwmaniish opened on Aug 25, 2026
  1

• duration humanize ignoring leap years

  iamkun/dayjs#3170 · Filter by author zac-robinson opened on Aug 6, 2026

• reproductible patch

  iamkun/dayjs#3163 · Filter by author bastien-roucaries opened on Jul 18, 2026

• Incorrect time separator for tzl locales

  iamkun/dayjs#3143 · Filter by author rahulpratik opened on Jun 16, 2026
  1

• Incorrect time separator for sv-fi locale

  iamkun/dayjs#3142 · Filter by author rahulpratik opened on Jun 16, 2026
  2

• Incorrect time separator for jv locale

  iamkun/dayjs#3141 · Filter by author rahulpratik opened on Jun 16, 2026
  3

• Incorrect time separator for ms and ms-my locales

  iamkun/dayjs#3139 · Filter by author rahulpratik opened on Jun 16, 2026
  3

• subtract(years) causes incorrect date when crossing historical timezone change in Malaysia

  iamkun/dayjs#3137 · Filter by author liangpishu opened on Jun 16, 2026
  1

• dayjs.tz(ms, 'UTC').startOf('day') returns prior-day UTC midnight on hosts with DST

  iamkun/dayjs#3123 · Filter by author bluepnume opened on Jun 9, 2026