mythologicalStartDateInGregorian

Given a predicate that represents a relationship or action between entities, generate a one-sentence description explaining its meaning.  
# Instructions
Focus on describing the relationship, not the entities themselves. 
# Response Format
Begin the description with \' Indicates...\'

Predicate: mythologicalStartDateInGregorian

Indicates the date, expressed in the Gregorian calendar, on which a mythological event, era, or figure is considered to have begun.