The keyword `ago` behaves differently here than in GNU date.

[yuankunzhang]

Problem

In this implementation, ago may appear only once -- at the end of the entire expression -- and its effect is global, reversing all preceding date‑time displacements as a single group.

GNU date treats ago as a local modifier: it can follow any individual displacement, may be used multiple times in the same expression, and applies only to the displacement that immediately precedes it.

Examples

$ date
Tue Apr 22 10:06:38 PM +08 2025

$ date -d '2 days 3 days ago'
Mon Apr 21 10:07:03 PM +08 2025
$ coreutils date -d '2 days 3 days ago'
Thu Apr 17 22:07:14 UTC 2025

$ date -d '2 days ago 3 days ago'
Thu Apr 17 10:08:33 PM +08 2025
$ coreutils date -d '2 days ago 3 days ago'
date: invalid date '2 days ago 3 days ago'