gnucompability(date): when -d is "EST EST" it accepted but gnu one rejected it

Hi, uutils mainteners

that is a compability issue, as our test confirmed

```css
relunsec@relunsec:~/software/coreutils/target/debug$ ./date -d "EST EST" 
Sun Jun 14 01:00:00 AM EDT 2026
```

it accepted while gnu one rejects it

```css
relunsec@relunsec:~/software/coreutils/target/debug$ gnudate -d "EST EST" 
gnudate: invalid date ‘EST EST’
```