bug(date): some valid dates like "@253402300739" and MEST prefix if before not after are rejected however the gnu one accepts them

[HackingRepo]

Hi, uutils mainteners

that is a FP with the date command as confirmed in the test

relunsec@relunsec:~/software/coreutils/target/debug$ ./date -d "@253402300739" 
date: invalid date '@253402300739'
relunsec@relunsec:~/software/coreutils/target/debug$ gnudate -d "@253402300739" 
Fri Dec 31 06:58:59 PM EST 9999
relunsec@relunsec:~/software/coreutils/target/debug$ 

that is a valid date and accepted perfectly by gnu but uu one errors out

then also the MEST prefix not accepted by uu date while the gnu date does

relunsec@relunsec:~/software/coreutils/target/debug$ ./date -d "MEST 2026-06-15"
date: invalid date 'MEST 2026-06-15'
relunsec@relunsec:~/software/coreutils/target/debug$ gnudate -d "MEST 2026-06-15"
Sun Jun 14 06:00:00 PM EDT 2026
relunsec@relunsec:~/software/coreutils/target/debug$