Editing Doomsday rule (section)

==Full examples==

===Example 1 (1985)===
Suppose we want to know the day of the week of September 18, 1985. We begin with the century's anchor day, Wednesday. To this, add {{math|''a''}}, {{math|''b''}}, and {{math|''c''}} above:

*{{math|''a''}} is the floor of {{math|{{sfrac|85|12}}}}, which is 7.
*{{math|''b''}} is {{math|85 mod 12}}, which is {{math|1}}.
*{{math|''c''}} is the floor of {{math|{{sfrac|''b''|4}}}}, which is 0.

This yields {{math|''a'' + ''b'' + ''c'' {{=}} 8}}. Counting 8 days from Wednesday, we reach Thursday, which is the doomsday in 1985. (Using numbers: In modulo 7 arithmetic, 8 is congruent to 1. Because the century's anchor day is Wednesday (index 3), and 3 + 1 = 4, doomsday in 1985 was Thursday (index 4).) We now compare September 18 to a nearby doomsday, September 5. We see that the 18th is 13 past a doomsday, i.e. one day less than two weeks. Hence, the 18th was a Wednesday (the day preceding Thursday). (Using numbers: In modulo 7 arithmetic, 13 is congruent to 6 or, more succinctly, −1. Thus, we take one away from the doomsday, Thursday, to find that September 18, 1985, was a Wednesday.)

===Example 2 (other centuries)===
Suppose that we want to find the day of week that the [[American Civil War]] broke out at [[Fort Sumter]], which was April 12, 1861. The anchor day for the century was 94 days after Tuesday, or, in other words, Friday (calculated as {{math|18 × 5 + ⌊{{sfrac|18|4}}⌋}}; or just look at the chart, above, which lists the century's anchor days). The digits 61 gave a displacement of six days so doomsday was Thursday. Therefore, April 4 was Thursday so April 12, eight days later, was a Friday.