EasterSundayGreekOrthodox[year] gives the date of Easter Sunday according to the Greek Orthodox Church using the Gregorian system.

EasterSunday[year] gives the date of Easter Sunday in the Gregorian calendar system.

ApproximateVertexCover[g] produces a vertex cover of graph g whose size is guaranteed to be within twice the optimal size.

Automorphisms[g] gives the automorphism group of the graph g.

CartesianProduct[l_1, l_2] gives the Cartesian product of lists l_1 and l_2.

CliqueQ[g, c] yields True if the list of vertices c defines a clique in graph g.

Cofactor[m, {i, j}] calculates the (i, j)\[Null]^th cofactor of matrix m.

ConstructTableau[p] performs the bumping algorithm repeatedly on each element of permutation p, resulting in a distinct Young tableau.

CostOfPath[g, p] sums up the weights of the edges in graph g defined by the path p.

CyclicGroup[n] returns the cyclic group of permutations on n symbols.