I can see for AGL the Ex dividend date was 24 Feb 2021 & Payment Date was 26 Mar 2021. When will they pay the 2nd payment of dividend & will there be a new Ex Dividend Date for the 2nd lot of dividend payment.
Usually there are two dividends per year (not guaranteed) Interim and Final and usually about 6 months apart. Some companies pay quarterly. If you search on the net you can get all sorts of history of dividend paying companies and can roughly figure their dates.