NiFi is designed to accept many triggers words sec, second, secs, seconds, min, minutes, mins, hr, hrs , day, days, etc....
The max it will accept as of NiFi 1.x is week or weeks (or wk or wks).
If you enter an invalid trigger word, the processor will let you know it is invalid. Such as trying to use month or year will produce the below:
Keep in mind that by using the "timer driven" scheduling strategy you are not setting a specific execution time. You are setting an execution interval where the first interval is scheduled upon start of the processor. The second execution will occur x amount of configured "run schedule" later. If you stop and then start the processor again, the interval starts over.
The "CRON Driven" scheduling strategy allow you to configure an exact time(s) for execution.
Thanks,
Matt
