Delaying a task by some time

Hello, I am written a POU controlled by task that runs every 30 seconds. What I want is that task should be delayed by 15 sec before its first start. i.e. POU will be called at 0.15,0.45,1.15,1.45,2.15,2.45....

How can I do it?

Use a 10 second timer to start a 5 second timer. When the 5 second timer is done begin your sequence.
Or maybe use 1/2 of the 30 second timer to begin the sequence. That should be less programming if you are using C#.

Depending on you platform, there should be system functions that will allow you to disable and enable a task. In your init code, disable the task, and have a separate bit of code that enables it after 15 seconds.

Depending on your platform, that may not work. The task might be assigned it's time slot at boot with no way to move it. In that case, you'll have to run it on a 15second cycle and use a flag to jump to the end every other cycle.

use task configuration and put a task on #t15s, under this task your POU.
put in the pou a flipflop to prevent it running all the time.
if unit has RTC also possible to check on time.