Hi,

to get the start time of a linux process in an human readable format use the user-defined format of ps with the lstart option.

For examble: This shows the command line, the pid and the process start time of the process id 921.

michael@debdev ~ # ps -eo pid,lstart,cmd -q 921
  PID                  STARTED CMD
  921 Fri Jan 23 09:19:01 2020 /usr/bin/java

Michael