Convert formatted dates to seconds since the epoch

I have a file:

pablo tty8 Thu Nov 1 12:51:21 2012 still logged in 
(unknown tty8 Thu Nov 1 12:50:57 2012 - Thu Nov 1 12:51:21 2012 (00:00) 
pablo tty2 Thu Nov 1 12:50:39 2012 still logged in 
pablo tty7 Thu Nov 1 12:49:45 2012 - Thu Nov 1 12:50:56 2012 (00:01) 
(unknown tty7 Thu Nov 1 12:34:32 2012 - Thu Nov 1 12:49:45 2012 (00:15)

I want to replace the file in the above date for a second. I want to print:

pablo tty8 1351770681 still logged in 
(unknown tty8 1351770657 - 1351770681 (00:00) 
pablo tty2 1351770639 still logged in 
pablo tty7 1351770585 - 1351770656 (00:01) 
(unknown tty7 1351769672 - 1351770585 (00:15)

I tried this command:

gawk --posix 'function my()
{"date -d \047"$0"\047 +%s" | getline b; 
gsub( /[A-Za-z]{3} [A-Za-z]{3} [0-9] ([0-9]{2}:){2}[0-9]{2} [0-9]{4}/,b );print}
{ my() }' file

The above command does not work:

$ gawk --posix 'function my()
> {"date -d \047"$0"\047 +%s" | getline b; 
> gsub( /[A-Za-z]{3} [A-Za-z]{3} [0-9] ([0-9]{2}:){2}[0-9]{2} [0-9]{4}/,b ); print}
> { my() }' ta
date: błędna data: `pablo tty8 Thu Nov 1 12:51:21 2012 still logged in '
pablo tty8  still logged in 
(unknown tty8 1351897200 - 1351897200 (00:00) 
date: błędna data: `pablo tty2 Thu Nov 1 12:50:39 2012 still logged in '
pablo tty2 1351897200 still logged in 
date: błędna data: `pablo tty7 Thu Nov 1 12:49:45 2012 - Thu Nov 1 12:50:56 2012 (00:01) '
pablo tty7 1351897200 - 1351897200 (00:01) 
(unknown tty7 1351897200 - 1351897200 (00:15)

How to improve the above command?