On 2 May 1990, a five-judge Constitution Bench distilled the law of seniority into eleven propositions — holding that seniority counts from the date of appointment according to rule, not confirmation, and that continuous officiation till regularisation counts towards seniority.
On 11 March 2026, a Supreme Court bench of Justices Rajesh Bindal and Vijay Bishnoi held in M. Thanigivelu v. Tamil Nadu Electricity Board that training is part of the service for the purposes of seniority — and that an administrative Board Proceeding cannot retrospectively re-date the seniority of direct recruits to align them with promotees. The judgment restates a longstanding service-jurisprudence principle in the language of the TNEB Service Regulations and clarifies the limits on the State employer's discretion to reorder service hierarchies through administrative instruments.