Start by working out the numerical value for the month. Under Zeller's formula, each month is given a number, with March being 1, April being 2 and so on until February is 12. For the purposes of this formula, January and February are the last months of the previous year, so February 2006 is the 12 month of 2005. Using the example March 10, 2011, March is 1.
Multiply the number value for the month by 13. Subtract 1 from the total and divide by 5. So in the example where March is 1, it is: 1 x 13 - 1 = 12; 12 divided by 5 is 2.4. In Zeller's formula, all numbers after the decimal are ignored, so the month value for March is 2.
Take the last two digits of the year, in this case 11, and add one quarter to the total. One quarter of 11 is 2.75, so the total is 13.75. Again, ignore the numbers after the decimal point, and you have 13.
Determine what is one-quarter of the first two digits of the year. In the 21st century, this is always 5. In the 20th century, this is 4.75, which is 4 under Zeller's formula. Subtract from this double the first two numbers of the decade. For the 21st century, you get -35 (5 - 40). For the 20th century, you get -34.
Add the day of the month to all of the other numbers. For example, for the date March 10, 2011, add 10 + 2 + 13 + -35 = -10. Your end result in this case is -10 (it can be a positive number in other cases).
Divide the result by 7 and find the remainder. If the number is a negative, then you have to find the nearest integer divisible by 7 that is less than the number. With the -10 result, -14 is the nearest integer divisible by 7 that is less than -10. The remainder is 4.
Use the remainder to find the day of the week. Zero corresponds to Sunday, 1 to Monday, 2 for Tuesday and so on. For example, the remainder of 4 corresponds to Thursday, so March 10, 2011. is a Thursday.