I have a column with data as shown below:

1 Jun 2007 06:00:50:000
1 Jun 2007 06:00:55:000
1 Jun 2007 06:01:00:000
1 Jun 2007 06:01:05:000
1 Jun 2007 06:01:10:000



I would like to format this data so that I can call the first data point (1
Jun 2007 06:00:50:000) as 0 seconds, and the following data points as 5
seconds, 10 seconds etc). The data is not all exactly separated by 5
seconds. I have some 45000 rows of data.