How to get the Firebird server date and time?

There are two variables available, CURRENT_DATE which returns the current date and CURRENT_TIMESTAMP which returns date and time. You can use those in SQL statements:

insert into t1 values(10, CURRENT_TIMESTAMP);

To query the current time, use this:

select current_date, current_timestamp
from rdb$database;

You need to select from something and rdb$database is a convenient one-row table that is present in each database.

You can also assign those variables in PSQL (stored procedure and trigger language):

create procedure p1
as
BEGIN
if (current_timestamp > cast('2007-11-03' as timestamp)) then
exception myerror;
...
END

It should be noted that CURRENT_TIMESTAMP returns the timestamp of statement start, which means it is constant during the statement execution. If you need the exact timestamp of that very moment, use a special value 'now'. If you want to select it, you need to cast it to timestamp explicitly. Without CAST you would get char(3) string 'now' instead. If you assign it to a timestamp variable or compare with some column, the required datatype is known so there is no need for casting.

select cast('now' as timestamp), cast('today' as date)
from rdb$database;


set term ^ ;
execute block returns (ts timestamp, dt date) as
begin
ts = 'now';
if (ts = 'now') then dt = 'today';
suspend;
end


SELECT *
FROM EMPLOYEE
WHERE HIRE_DATE < 'today'

As you can see, the same rule applies for CURRENT_DATE, and you can use a special value 'today', to get the current value. Beside that, you might also find 'tomorrow' and 'yesterday' useful.

The reason behind all this is that statements should be atomic, so CURRENT_DATE and CURRENT_TIMESTAMP provide consistency. If statement execution takes a long time it can easily happen that the date changes between statement start and end.