Zeller's congruence [SEP] discoverer or inventor
Zeller's congruence
Zeller's congruence is an algorithm devised by Christian Zeller to calculate the day of the week for any Julian or Gregorian calendar date. It can be considered to be based on the conversion between Julian day and the calendar date.
Formula.
For the Gregorian calendar, Zeller's congruence is
for the Julian calendar it is
where 
- "h" is the day of the week (0 = Saturday, 1 = Sunday, 2 = Monday, ..., 6 = Friday)
manifolds), in the theory of smooth manifolds, the set of integral curves defined by a nonvanishing vector field defined on the manifold
- Congruence (general relativity), in general relativity, a congruence in a four-dimensional Lorentzian manifold that is interpreted physically as a model of space time, or a bundle of world lines
- Zeller's congruence, an algorithm to calculate the day of the week for any date
- Scissors congruence, related to Hilbert's third problem
Psychology.
- In Carl Rogers