When did they start EPNS I have a tea strainer with this on the bottom and been told from Is possible?

EPNS, or electroplated nickel silver, was developed in the electroplating industry in the early 19th century. It was a process that involved electroplating a thin layer of nickel onto a base metal, usually copper or brass. This provided the metal with a lustrous silver-like finish that was more durable and resistant to wear and tarnishing than the base metal itself.

So it's possible that your tea strainer with the "EPNS" mark on the bottom could indeed date from this time period, making it a potential antique or vintage piece.