the Last date for conducting AGM is 30th September of every yr(without extension). There should be 21 clear days notice for AGM. Hence you can assume any date(after considering 21 clear days) as the Board meeting date.
However, there are special provisions for shorter notice also, wherein 95% of Shareholders shall give their assent.
Provided that in case of the first annual general meeting, it shall be held within a period of nine months from the date of closing of the first financial year of the company and in any other case, within a period of six months, from the date of closing of the financial year :
first AGM shall be held within 9 months from end of the financial yr. ie. if Co. is incorporated on 01.12.18 then due date for first AGM will be 12.12.19.
conclusion: for First AGM - 9 months from end of FY subsequent AGM- 6 months from end of FY.