Someone smart in biology, please answer this question on cell division!?

When does a cell become haploid? Is it that in the later part of interphase, chromosomes duplicate forming haploid cells? And in the telophase stage of mitosis, are the 2 nuclei haploid or diploid? If they're haploid, do they become diploid at their end of interphase? If so, how come during MEIOSIS, the newly formed zygote is haploid, shouldn't it be diploid first, undergo interphase, and then become haploid?