OrthodoxPascha.org

1. Calculate alpha and beta as follows:
Divide the year by 28 and the remainder (0 to 27) will be the alpha (red values on the Church Calendar Dial) used in step 3 below.
Divide the year by 19 and the remainder (0 to 18) will be beta (blue values on the Church Calendar Dial) used in step 5 below.

2. Initialize the Church Calendar Dial and Hexaemeron gear as follows: (see image)
Set the input (top middle of the Church Calendar Dial) to 'alpha.8 beta.1'
Set the output (bottom middle of the Hexaemeron gear) to 'K' (Kyriaki, 'Day of The Lord' = Sunday).

3. Dial alpha on the Church Calendar Dial. The Hexaemeron gear output will be the day of the week of Evangelismos (Annunciation).

4. Initialize the Church Calendar Dial as follows:
Set the input (top middle of the Church Calendar Dial) to 'alpha.8 beta.1' while holding the Hexaemeron gear so that it does not move.
Note. We do not have to perform step 4 if Evangelismos is on a Sunday, but doing so will not affect the computation.

5. Dial beta on the Church Calendar Dial. The date (black) above beta on the Church Calendar Dial is the Paschal Moon.
The Hexaemeron gear output will be the day of the week of the Paschal Moon.  

6. Calculate Pascha. Place a finger on the Hexaemeron gear output. This represents the Paschal Moon date.
Navigate counterclockwise with the finger without moving the gears while counting the dates until arriving at the next Kyriaki ‘K’ (Sunday).
This date is The Great and Holy Pascha of The Lord+