https://community.cloudera.com/t5/Support-Questions/How-to-convert-unix-timestamp-to-datetime-in-Apache-NiFi/m-p/224741#M186605 <P> Hi <A nodeid="76211" rel="user" href="#">@Wojtek</A>,</P><P> I believe the problem is that the format() function works only with numbers. Your timestamp has a '.' (dot) which makes it interpret as a string.</P><P> To solve the problem I have adopted the following EL un a updateAttribute processor:</P><PRE>${ts:substringBefore('.'):append(${ts:substringAfter('.')}) :toNumber():format('MM/dd/yyyy HH:mm:ss.SSS') } <P></P><P>ts attribute contains this value 1518442283.483</P><P>the result is 02/12/2018 13:31:23.483</P><P>I hope I have been of help</P></PRE> Mon, 23 Apr 2018 17:42:19 GMT isoardi 2018-04-23T17:42:19Z