Pick a year, then

do some math to find

a day-of-the-week.

That's our "Doomsday".

Each month of that

year has a date we

can reference as the

same day-of-the-week

as that "Doomsday".

The base "century part" of 2017 is **2000**

The "year part" of 2017 is**17**

The base-doomsday for century 2000 is The "year part" of 2017 is

Now, complete this sum:

baseDoomsday | + | year | + | round↓( year ÷ 4 ) | = |

2 | + | 17 | + | round↓( 17 ÷ 4 ) | = |

2 | + | 17 | + | round↓( 4.25 ) | = |

2 | + | 17 | + | 4 | = 23 |

Now divide that total by 7 and get the remainder...

total | ÷ | 7 = |

23 | ÷ | 7 = 3 with remainder 2 |

So now we must see what date, in our month (Feb 2017), is a "Doomsday Tuesday".

The dooms

And now we know that

2/27/2017 was a Monday

TABLE X | |||

base centuries | base doomsday | ||

1500 | 1900 | 2300 | 3 |

1600 | 2000 | 2400 | 2 |

1700 | 2100 | 2500 | 0 |

1800 | 2200 | 2600 | 5 |

* You probably only need toremember the red years! |

TABLE Y | |

week day | day num |

Sun | 0 |

Mon | 1 |

Tue | 2 |

Wed | 3 |

Thu | 4 |

Fri | 5 |

Sat | 6 |

TABLE Z | |

Month | Doomsdate |

Jan | Jan 31st (or Jan "32nd" in leap years) |

Feb | Feb 28th (or Feb 29th in leap years) |

Mar | Mar "0th" |

Other odd# months | 4/4, 6/6, 8/8,10/10, and 12/12 |

Other even# months | 5/9, 7/11, 9/5, and 11/7(Remember: "I work 9-to-5 at the 7-11") |