# Date Processing

## Test Cases

| Test ID | Description |
|---------|-------------|
| D-N001 | YYYYMMDD basic processing (parse year/month/day) |
| D-N002 | Leap year detection (2000=leap, 2100=no, 2024=leap, 2025=no) |
| D-N003 | Month-end days (Jan 31, Feb 28/29) |
| D-N004 | Date comparison (<, >, =) |
| D-A001 | FUNCTION INTEGER-OF-DATE date arithmetic (21 day diff) |
| D-A002 | Date arithmetic with FUNCTION DATE-OF-INTEGER |
| D-A003 | Invalid dates (Feb 30, Apr 31) |
| D-A004 | 2-digit year (YYMMDD) ambiguity |
| D-W001 | Japanese era: Reiwa R010501 = 2019/05/01 |
| D-W002 | Japanese era: Heisei H010108 = 1989/01/08 |
| D-W003 | Reiwa 6 (R060101 = 2024/01/01) |
| D-W004 | Showa era (S640101 = 1989/01/01) |
| D-W005 | Format conversion YYYYMMDD to YYMMDD |
| D-W006 | YYYYMMDD to Wareki string |
| D-W007 | Cross-era date comparison |
| D-F001 | FUNCTION CURRENT-DATE |
| D-F002 | Century boundary handling |
| D-F003 | Julian date format |

## Features Covered
- YYYYMMDD and YYMMDD processing
- Leap year rules (divisible by 400 vs 100)
- Month-end calculation
- FUNCTION INTEGER-OF-DATE / DATE-OF-INTEGER for arithmetic
- Date comparison operators
- Invalid date storage
- Japanese era (Wareki) representation: Reiwa/Heisei/Showa
- Format conversion between date representations

## Expected Results
All 18 tests should display PASS.