All of the calculations are done using whole numbers. Whenever you are asked to divide and keep only the whole number, simply ignore the decimal part. For example, in Step 2, you are asked to divide the year by 4. If the year were 2007, this would give 501.75, but you ignore the decimal part and write only 501.

Some steps ask you to divide one number by another and write down the remainder. Suppose you are asked to divide 33 by 7 and write down the remainder. First, divide 33 by 7 to get 4 plus a decimal part. Now subtract 4 times 7 from 33 to get 5. That is the remainder.

Instructions | For 2015 | For your year |
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Step 1: Preparations |
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Write the year. | 2015 | |

Divide the year by 100 and keep only the whole number. This is the Century Number. Call it C. |
C = 20 |
C = |

Subtract 15 from C and multiply the result by 3. | 15 | |

Divide the previous line by 4 and keep only the whole number. | 3 | |

Add 10 to the previous line. This is the Gregorian Correction. Call it Q. |
Q = 13 |
Q = |

Step 2: The Dominical Number |
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Divide the year by 4 and keep only the whole number. | 503 | |

Add the year to the previous line. | 2518 | |

Add 4 to the previous line. | 2522 | |

Subtract Q from the previous line. | 2509 | |

Divide the previous line by 7 and write down the remainder. | 3 | |

Subtract the previous line from 7. This is the Dominical Number. Call it L. |
L = 4 |
L = |

Step 3: The Golden Number |
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Divide the year by 19 and write down the remainder. | 1 | |

Add 1 to the previous line. This is the Golden Number. Call it G. |
G = 2 |
G = |

Step 4: The Julian Epact |
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Multiply the Golden Number, G, by 11. | 22 | |

Subtract 10 from the previous line. | 12 | |

Divide the previous line by 30 and write down the remainder. This is the Julian Epact. Call it J. |
J = 12 |
J = |

Step 5: The Solar Equation |
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Subtract 10 from the Gregorian Correction, Q. This is the Solar Equation. Call it S. |
S = 3 |
S = |

Step 6: The Lunar Equation |
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Subtract 14 from the Century Number, C. | 6 | |

Multiply the previous line by 8. | 48 | |

Divide the previous line by 25 and keep only the whole number. This is the Lunar Equation. Call it M. |
M = 1 |
M = |

Step 7: The Epact |
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Subtract the Solar Equation, S, from the Julian Epact, J. | 9 | |

Add the Lunar Equation, M, to the previous line. | 10 | |

If the previous line is zero or negative, add 30 to it. Repeat if necessary, until you get a positive number. | 10 | |

Divide the previous line by 30 and write down the remainder. This is the Epact. Call it E. |
E = 10 |
E = |

Step 8: The "Second Epact 25" rule |
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If the Golden Number, G, is more than 11 and the Epact is 25, change the Epact to 26. |
E = 10 |
E = |

Step 9: The "Epact 24 is equivalent to Epact 25" rule |
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If the Epact is 24, change the Epact to 25. | E = 10 |
E = |

Step 10: The date of the Paschal Full Moon |
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If the Epact, E, is less than 24, subtract E from 44, otherwise subtract E from 74. Call this D. | D = 34 |
D = |

If D is less than 32, then the Paschal Full Moon falls on that day in March. If D is 32 or larger, then subtract 31 from D, and the Paschal Full Moon falls on that day in April. |
April 3 | |

Step 11: The day of the week of the Paschal Full Moon |
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Add 10 to D. | 44 | |

Subtract the Dominical Letter, L, from the previous line. | 40 | |

Divide the previous line by 7 and write down the remainder. | 5 | |

Add 1 to the previous line. | 6 | |

The previous line gives the day of the week on which the Paschal Full Moon falls, where Sunday is the first day of the week. | Friday | |

Step 12: The date of Easter |
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Easter is the Sunday following the day of the Paschal Full Moon. |
April 5 |

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Last modified on 22 November 2014

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