Salesforce Cron expression for Scheduling the Job

In Salesforce, you can use cron expressions to schedule jobs to run at specific times or intervals. Cron expressions are strings comprised of six or seven fields that represent various components of time (seconds, minutes, hours, days, months, and optionally, years). 

Apex Scheduler

Note

Salesforce schedules the class for execution at the specified time. Actual execution can be delayed based on service availability.The System.schedule method uses the user's timezone for the basis of all schedules.

Here's the format:

Seconds Minutes Hours Day_of_month Month Day_of_week Optional_year

The following are the values for the expression:

The special characters are defined as follows:

The following are some examples of how to use the expression.

Here are some examples of cron expressions commonly used for scheduling jobs in Salesforce:

Every day at midnight:

0 0 0 * * ?

Every hour:

0 0 * * * ?

Every 15 minutes:

0 0/15 * * * ?

Every weekday at 9 AM:

0 0 9 ? * MON,TUE,WED,THU,FRI

Every 30th minute of every hour from 8 AM to 5 PM on weekdays:

0 30 8-17 ? * MON,TUE,WED,THU,FRI

Every Sunday at 6:30 PM:

0 30 18 ? * SUN

Every 10 minutes on the 15th day of every month:

0 0/10 * 15 * ?

When scheduling jobs programmatically in Salesforce using System.schedule, you would use cron expressions to specify the desired schedule. For example:

String jobName = 'MyScheduledJob';

String cronExp = '0 0 0 * * ?'; // Every day at midnight

MySchedulableClass myJob = new MySchedulableClass();

System.schedule(jobName, cronExp, myJob);

Please make sure to adjust the cron expression according to your specific scheduling requirements.