(Q91345841)
Statements
28 year
0 references
1200
0 references
cycle of 7-day weeks in a solar calendar over 28 years (Gregorian and Julian dominical cycles first matched on a secular leap year in 1200 AD, with dominical letter BA and a gap of 7 days between their dates)
![{\displaystyle {\begin{aligned}\mathrm {DL} &=DL[(y{\bmod {7}}+y{\bmod {4}})\times 2{\bmod {7}}],\\&{\begin{cases}DL[0]=\mathrm {'G'} ,\quad DL[1]=\mathrm {'F'} ,\quad DL[2]=\mathrm {'E'} ,\\DL[3]=\mathrm {'D'} ,\quad DL[4]=\mathrm {'C'} ,\quad DL[5]=\mathrm {'B'} ,\\DL[6]=\mathrm {'A'} .\end{cases}}\end{aligned}}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/e1ece7df4fb2d34233186c448e465bcdd7817d57)