Hi,
As your attorney, and on the facts you have provided, my short opinion is that you are likely to meet the age-relaxation requirement for “Central Government civilian employees who have rendered not less than three continuous regular years’ service as on the closing date.” You have already served well in excess of three years in regular central service and the single-day gap between appointments will not, in ordinary administrative practice, break continuity; therefore continuity and regularity are satisfied as a practical matter. The decisive remaining issue is whether the recruiting authority will regard your current post in the autonomous central institute as “Central Government” service for the specific recruitment notification at hand.
By the phrase “Central Government Civilian Employees who have rendered not less than 3 continuous regular years’ service as on the closing date” the requirement is that the service be substantive (regular, not ad-hoc or purely contractual) and unbroken as of the closing date; administrative practice accepts short re-appointment gaps (commonly up to a year) as preserving continuity, so a one-day gap is effectively immaterial. Whether time served in an autonomous central institute counts depends on the recruitment notification and the administrative/legal status applied by the recruiting authority: some notifications expressly include employees of central autonomous bodies, some are silent and applied flexibly, and some are read narrowly to mean only those on direct Central Government establishment — thus the text of the advertisement and any controlling ministry/DoPT guidance for that vacancy will control.
Practical next steps you should take immediately are to check the exact wording of the recruitment advertisement for any express inclusion or exclusion of autonomous bodies, obtain (and retain) all documentary proof of appointment, relieving, joining orders, service certificates and pay records showing regular status and the one-day gap, and seek a written clarification from the recruiting authority if the notification is ambiguous; if you receive a written denial, insist on the specific rule or precedent relied upon because administrative representation and, if necessary, judicial review are available remedies. If you wish, I will draft either (A) a short representation/clarification letter to the recruiting authority or (B) a concise checklist and declaration you can attach to your online application, tell me which and I will prepare the draft for your review. Reach out to me on adv.vishesh@icould.com for further help.