Index Guidelines

Hi folks, ya all are just fine i hope.
I've a question regarding indexes.
I've a table that is very often updated. My boss asked me to keep a log of each record when the table is updated. I've created an AFTER UPDATE trigger on the table and throw the old record into a log table on each update. The table would get large earlier. I want the updates on the original table fast, so i don't wanna add any kind of indexes on the log table. The log table will be scarcely queried only if the user has made a mistake and we want the old record back.
Now, i've column named event(DATETIME) log table that records CURRENT_TIMESTAMP. Should i create a clustered index on this column so the records get in sequence (the values in the column will be unique due to time and seconds being stored). I could be able to access records fastly in the log table on the basis of EVENT column. But how much it would cost the updates on the original table??
My major concern is to keep the updates on original table fast while logging the old records.
Usually it's said not to created indexes on date fields. Do i need to create non-clustered index or i am following the correct path.


Any tips and guidlines; highly appreciated.


Howdy!