Update Only Date

I have a table with column datetime which has value as follows

31/03/2011 11:59:00 PM

Without distrubing the time, I only want to change the date portion as 31/12/2020

how do i do this
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Naveen KumarProduction Manager / Application Support ManagerCommented:
try this :

update your_table
set date_column = to_date( '31-Dec-2020' || to_char(date_column,'HH:MI:SS AM'),
'dd-Mon-yyyy HH:MI:SS AM')
where <<use accordingly >>>;

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update table_name set date_column = date_column + (to_date('31-12-2020','DD-MM-YYYY') - to_date('31-03-2011','DD-MM-YYYY'))

The expression after the plus sign just gets the number of days between the two dates, which is then added to your date_column.  You will be adding whole days, so the time should not change.
oh yes of course you need to add a where clause.

update <you table name> a
set a.<date column name>=to_date((
select '31/12/2020 ' ||  to_char(b.<date column name>,'HH:MI:SS')
from <you table name> b where a.<key column(s)>=b.<key column(s)>

Naveen KumarProduction Manager / Application Support ManagerCommented:
Good and thanks
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