well it depends on how you are defining / designing these jobs. I mean are you planning to put them in BOX or out of box.
Hope you are aware of BOX job features and how Box and JObs inside BOX will behave?
If in BOX, then you can put the run frequency on BOX.
BOX_ABC -> runs daily at 1AM
JOB A -> not need to put any schedule and it will run immediately as soon as BOX comes to RUNNING STATE at 1AM
JOB B -> Here you can put time dependency of 8PM, then the BOX will be in running state till 8PM.
JOB C -> conditions: s(JOB A) & s(JOB B). Here as soon as JOB B completes(SUCCESS) its 8PM run, JOB c will run.
Here in this scenario, since you have different start times of jobs involved, I would not suggest to go for BOX feature as BOX job has some unique features or behavior which can complicate the situation during abnormal situations(like long running, missing its run window etc) or adhoc runs.
I would go for OUT of BOX concept, where all 3 jobs will run as per there run frequency and float the conditions in the autosys envt to trigger the dependency.
JOB A -> Define to run at 1AM.
JOB B -> Here you can put time dependency of 8PM.
JOB C -> conditions: s(JOB A) & s(JOB B). Here as soon as JOB B completes(SUCCESS) its 8PM run, JOB c will run.
Defining these kind of scenarios like this (OUT of box) will ease the operations in abnormal situations(like long running, missing its run window etc) or adhoc runs.
Request you to go through BOX feature / BOX behavior in details before actually using BOX jobs if you are new to AUTOSYS or BOX jobs. UNICENTRE AUTOSYS 4.0 version documentation is best reference to UNDERSTAND in detail on BOX jobs.
Hope it will clarify your question and ease the scheduling SCENARIOS.