Need Cron Expression to run scheduler every 3 hours starting at 3 am

Question

I need cron expression for quartz scheduler to run scheduler every 3 hours starting at 3 am. I tried below, however it is skipping 12 am run everyday. 0 0 3/3 * * ?

I am unable to understand what exactly needs to be modified in above to get that 12 am run as well. Kindly help.

Answer 1

try 0 0 3,6,9,12 * * ? . can read the official doc , get more information about the expression .

Answer 2

It should be

0 0 3/3 ? * * *

You can use online cron makers to validate / construct crons. Here is a handy tool https://www.freeformatter.com/cron-expression-generator-quartz.html

Answer 3

You can try:

1 3/3 * * *

This translates to "At minute 1 past every 3rd hour from 3 through 23". Crontab.guru is an excellent resource.