BSD-3-Clause licensed by Bryan O'Sullivan
Maintained by Adam Bergmark
This version can be pinned in stack with:attoparsec-iso8601-,1453

Module documentation for

Parsing of ISO 8601 dates.

This package is used to parse dates in aeson. It is split into a separate package to be shared by other projects that want to parse dates like aeson does.

For now, this project is located in the aeson repository and aeson itself uses the source of this package without pulling in the package as a dependency.


Since aeson depends on this package we want to be very careful about changing the format.

There may be breaking changes if we find that the format is incorrectly too lenient. We consider widening of the allowed input a non-breaking addition since all previously valid input will still parse correctly.


For the latest version of this document, please see

  • Support GHC-8.6.5…9.10.1

  • Change parsers of types with year (Day, UTCTime) to require years with at least 4 digits.
  • Remove fast and developer package flags

  • Code (re)organization.
  • Avoid wildcard imports

  • Add month :: Parser Month and quarter :: Parser Quarter

  • Fixes handling of UTCTime wrt. leap seconds , thanks to Adam Schønemann