Date functions in PostgreSQL , Time functions in PostgreSQL

This is very basic. I want to replace all the occurrences of a particular date with another date in a column. How to do it?

unsa , wa ko sabot nimu?

is there any query for applying to total column , i mean like taking a column full of dates and getting anouther column using that to fill it with functions like date of the month or day of the year and like that ??

hello sir , i am looking for pg training online / class room . i am form hyd.

Nice stuff

Good explanation...