RR MILLENNIUM equivalent in Postgres - postgresql

Question

Is there a built in function in PostgreSQL 9.5 version to calculate the appropriate century/millenium?
When I use birth_date::TIMESTAMP from a table, sometimes it prefix 19 and sometimes it prefix 20. Below example
Input:
28JUN80
25APR48
Output:
"1980-06-28 00:00:00"
"2048-04-25 00:00:00"
I also have records in the table with birth_date holding values like "07APR1963" which gets computed appropriately as "1963-04-07 00:00:00".
I need use CASE statement when the length is 7 characters, then prefix with 19 millennium and when its 9 characters, just load it as it is.

Answer 1

https://en.wikipedia.org/wiki/Unix_time Unix epoch is
beginning (00:00:00 1 January 1970)
So if you don't specify the century, but just last YY it will be 20th century from 00:00:00 1 January and 21st century before YY equal 70. If you want it to guess the 20th century either append year as you do, or specify CC, eg:
t=> select
to_timestamp('1JAN70', 'ddmonYY')
, to_timestamp('31DEC69', 'ddmonyy')
, to_timestamp('31DEC69 20', 'ddmonyy cc');
to_timestamp | to_timestamp | to_timestamp
------------------------+------------------------+------------------------
1970-01-01 00:00:00+00 | 2069-12-31 00:00:00+00 | 1969-12-31 00:00:00+00
(1 row)
https://www.postgresql.org/docs/current/static/functions-formatting.html
In conversions from string to timestamp or date, the CC (century)
field is ignored if there is a YYY, YYYY or Y,YYY field. If CC is used
with YY or Y then the year is computed as the year in the specified
century. If the century is specified but the year is not, the first
year of the century is assumed.
update
So in your case you should do smth like:
vao=# create table arasu (member_birth_date character(9)); insert into arasu values ('28JUN80'),('25APR48');
CREATE TABLE
INSERT 0 2
vao=# select to_timestamp(member_birth_date||' 20', 'ddmonYY cc') from arasu;
to_timestamp
------------------------
1980-06-28 00:00:00+03
1948-04-25 00:00:00+03
(2 rows)