To make it simple. let it be mid October. However, this is my opinion that one must make use of early starting if the weather permits. It gives a head start, better hardiness for coming winter, longer time for biennials & perennials. All cool season annuals can be started together in mid October. Endeavor should be made to start biennials and perennials early that is only if you want them to flower in spring/early summer.
farhan or i better say mr.sheikh, what should be the sequence if i grow these in different kiyariz i mean from N->S if my lawn is S facing i guess that would be prioritized based on flower sizes to look good isn't it? hope u got what im trying to ask?