תחילת כהונה כיושב ראש מפלגת העבודה

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: תחילת כהונה כיושב ראש מפלגת העבודה

Indicates the date or event marking when someone begins their term as chairperson of the Labor Party.