When does DNA replication occur durring cell division

Well, sort of, but not really. There is a bit of ambiguity in what you mean by "cell division".

In eukaryotes (which I will assume you are studying cell division for), there are two main types of cell division: mitotic and meiotic.

For mitotic cell division, DNA replication occurs during the cell cycle, but in the S phase of interphase ... not during mitosis (nuclear division) or cytokinesis (division of the cytoplasm).

However, DNA replication is required in order for mitotic cell division to occur; and DNA replication doesn't begin until the cell has become 'committed' to entering mitosis.

For meiosis, DNA replication also occurs in the S phase of interphase, but only before the first round of cell division (associated with Meiosis I); before the second round of cell division (associated with Meiosis II), DNA replication does not occur.