uutils/coreutils

Date rejects valid large years that GNU date accepts

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#9774 opened on Dec 22, 2025

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U - datefuzzinggood first issue

Description

GNU:

  $ LANG=C TZ=UTC0 /usr/bin/date -d "18978-01-01"
  Thu Jan  1 00:00:00 UTC 18978

Rust:

  $ LANG=C TZ=UTC0 ./target/debug/date -d "18978-01-01"
  date: invalid date '18978-01-01'
  • GNU date: Accepts year 18978 and outputs the date correctly
  • Rust date: Rejects year 18978 as invalid date, appears to have a limit around year 9999
  • GNU date supports much larger year ranges than our implementation

Found with a fuzzer

Contributor guide

Tech stack
rust
Domain
cli
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Rust basicsunderstanding of date parsing
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75
Research direction
The issue is that the Rust date command rejects years beyond 9999, while GNU date accepts larger years like 18978. Start by locating the date parsing logic in the repository, likely in the 'src/uu/date' directory. Look for where the year range is validated or where a limit like 9999 is set. This might be in the implementation of parsing dates with chrono or custom logic. Compare with GNU's behavior to understand the expected range. Adjust the parsing to accept a wider range of years.