gnucompability(date): Edge Cases (Part 3)

Hi, uutils mainteners

here is our new tests

relunsec@relunsec:~/software/coreutils/target/debug$ ./date $'+%___B1e'
September1e
relunsec@relunsec:~/software/coreutils/target/debug$ gnudate $'+%___B1e'
September1e
relunsec@relunsec:~/software/coreutils/target/debug$ ./date $'+%___+1e'
+18
relunsec@relunsec:~/software/coreutils/target/debug$ ./date $'+%___-1e'
18
relunsec@relunsec:~/software/coreutils/target/debug$ gnudate $'+%___-1e'
18
relunsec@relunsec:~/software/coreutils/target/debug$ ./date $'+%___+1e'
+18
relunsec@relunsec:~/software/coreutils/target/debug$ gnudate $'+%___+1e'
18
relunsec@relunsec:~/software/coreutils/target/debug$ 

Another parser confusion

relunsec@relunsec:~/software/coreutils/target/debug$ ./date $'+%:::A'
Friday
relunsec@relunsec:~/software/coreutils/target/debug$ gnudate $'+%:::A'
%:::A
relunsec@relunsec:~/software/coreutils/target/debug$ 

Also another test

relunsec@relunsec:~/software/coreutils/target/debug$ gnudate $'+%_-######A'
FRIDAY
relunsec@relunsec:~/software/coreutils/target/debug$ ./date $'+%_-######eA'
18A
relunsec@relunsec:~/software/coreutils/target/debug$ 

also with

relunsec@relunsec:~/software/coreutils/target/debug$ ./date  -d "month next month"
Wed Nov 18 10:54:02 AM EST 2026
relunsec@relunsec:~/software/coreutils/target/debug$ gnudate  -d "month next month"
Wed Nov 18 09:54:05 AM EST 2026
relunsec@relunsec:~/software/coreutils/target/debug$ 

same with

relunsec@relunsec:~/software/coreutils/target/debug$ ./date  -d "next hour EST"
Fri Sep 18 01:05:41 PM EDT 2026
relunsec@relunsec:~/software/coreutils/target/debug$ gnudate  -d "next hour EST"
gnudate: invalid date ‘next hour EST’
relunsec@relunsec:~/software/coreutils/target/debug$ 

another one

relunsec@relunsec:~/software/coreutils/target/debug$ ./date --debug -d "yesterday Fri Oct  2 11:10:59 AM EDT 2026"
date: input string: yesterday Fri Oct  2 11:10:59 AM EDT 2026
date: parsed date part: (Y-M-D) 2026-10-01
date: parsed time part: 11:10:59
date: input timezone: system default
Thu Oct  1 11:10:59 AM EDT 2026
relunsec@relunsec:~/software/coreutils/target/debug$ gnudate --debug -d "yesterday Fri Oct  2 11:10:59 AM EDT 2026"
date: parsed relative part: -1 day(s)
date: parsed day part: Fri (day ordinal=0 number=5)
date: parsed date part: (Y-M-D) 2026-10-02
date: parsed time part: 11:10:59
date: parsed local_zone part: isdst=1
date: parsed number part: 
date: input timezone: system default, dst
date: error: seen multiple time parts
gnudate: invalid date ‘yesterday Fri Oct  2 11:10:59 AM EDT 2026’
relunsec@relunsec:~/software/coreutils/target/debug$ 

Here is another example

relunsec@relunsec:~/software/coreutils/target/debug$ ./date --debug -d "next day last tuesday 12:00:00 EST next day"
date: input string: next day last tuesday 12:00:00 EST next day
date: parsed date part: (Y-M-D) 2026-09-17
date: parsed time part: 13:00:00
date: input timezone: system default
Thu Sep 17 01:00:00 PM EDT 2026
relunsec@relunsec:~/software/coreutils/target/debug$ gnudate --debug -d "next day last tuesday 12:00:00 EST next day"
date: parsed relative part: +1 day(s)
date: parsed day part: last Tue (day ordinal=-1 number=2)
date: parsed time part: 12:00:00
date: parsed local_zone part: isdst=0
date: parsed relative part: +2 day(s)
date: input timezone: system default
date: using specified time as starting value: '12:00:00'
date: error: invalid date/time value:
date:     user provided time: '(Y-M-D) 2026-09-18 12:00:00'
date:        normalized time: '(Y-M-D) 2026-09-18 13:00:00'
date:                                             --
date:      possible reasons:
date:        nonexistent due to daylight-saving time;
date:        numeric values overflow;
date:        missing timezone
gnudate: invalid date ‘next day last tuesday 12:00:00 EST next day’
relunsec@relunsec:~/software/coreutils/target/debug$ 

also with

relunsec@relunsec:~/software/coreutils/target/debug$ gnudate -d "2023-01-05 09:05:07" --debug +%c
date: parsed date part: (Y-M-D) 2023-01-05
date: parsed time part: 09:05:07
date: input timezone: system default
date: using specified time as starting value: '09:05:07'
date: starting date/time: '(Y-M-D) 2023-01-05 09:05:07'
date: '(Y-M-D) 2023-01-05 09:05:07' = 1672927507 epoch-seconds
date: timezone: system default
date: final: 1672927507.000000000 (epoch-seconds)
date: final: (Y-M-D) 2023-01-05 14:05:07 (UTC)
date: final: (Y-M-D) 2023-01-05 09:05:07 (UTC-05)
gnudate: output format: ‘%c’
Thu 05 Jan 2023 09:05:07 AM EST
relunsec@relunsec:~/software/coreutils/target/debug$ ./date -d "2023-01-05 09:05:07" --debug +%c
date: input string: 2023-01-05 09:05:07
date: parsed date part: (Y-M-D) 2023-01-05
date: parsed time part: 09:05:07
date: input timezone: system default
Thu Jan  5 09:05:07 2023
relunsec@relunsec:~/software/coreutils/target/debug$ 

also

relunsec@relunsec:~/software/coreutils/target/debug$ gnudate --debug -d "2023-01-01 12:00:00 + 1 day"
date: parsed date part: (Y-M-D) 2023-01-01
date: parsed time part: 12:00:00 UTC+01
date: parsed relative part: +1 day(s)
date: input timezone: parsed date/time string (+01)
date: using specified time as starting value: '12:00:00'
date: starting date/time: '(Y-M-D) 2023-01-01 12:00:00 TZ=+01'
date: after date adjustment (+0 years, +0 months, +1 days),
date:     new date/time = '(Y-M-D) 2023-01-02 12:00:00 TZ=+01'
date: '(Y-M-D) 2023-01-02 12:00:00 TZ=+01' = 1672657200 epoch-seconds
date: timezone: system default
date: final: 1672657200.000000000 (epoch-seconds)
date: final: (Y-M-D) 2023-01-02 11:00:00 (UTC)
date: final: (Y-M-D) 2023-01-02 06:00:00 (UTC-05)
gnudate: output format: ‘%a %b %e %r %Z %Y’
Mon Jan  2 06:00:00 AM EST 2023
relunsec@relunsec:~/software/coreutils/target/debug$ ./date --debug -d "2023-01-01 12:00:00 + 1 day"
date: input string: 2023-01-01 12:00:00 + 1 day
date: parsed date part: (Y-M-D) 2023-01-02
date: parsed time part: 12:00:00
date: input timezone: system default
Mon Jan  2 12:00:00 PM EST 2023
relunsec@relunsec:~/software/coreutils/target/debug$ 

Start with the date command and reproduce the listed format-parser and -d parsing cases against GNU date, including the --debug output. Group the mismatches by parser behavior and add focused regression coverage for each case; done means the Rust date command matches the GNU results shown in the issue.