Decision table for determining the days in a month
M1 = {x: x is a 30-day month}
M2 = {x: x is a 31-day month}
M3 = {x: x is February}
| conditions | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 |
| C1. Is month in M1 ? | T | T | T | T | T | T | T | T | F | F | F | F | F | F | F | F |
| C2. Is month in M2 ? | T | T | T | T | F | F | F | F | T | T | T | T | F | F | F | F |
| C3. Is month in M3 ? | T | T | F | F | T | T | F | F | T | T | F | F | T | T | F | F |
| C4. Is year leap year ? | T | F | T | F | T | F | T | F | T | F | T | F | T | F | T | F |
| A1. last day = 30 | x | x | ||||||||||||||
| A2. last day = 31 | x | x | ||||||||||||||
| A3. last day = 28 | x | |||||||||||||||
| A4. last day = 29 | x | |||||||||||||||
| A5. Impossible | x | x | x | x | x | x | x | x | x | x |