I've setup a cron job that greps a file every five minutes and then writes (appends) the grep output/result to another file:

grep "monkey" zoo.log | tail -1 >> cron-zoo-log

Is there any way I can add the date and time (timestamp) to the cron-zoo-log file for each time a new line was added?

At the moment the cron-zoo-log just looks like this:

monkey house
monkey car

Could I get it to be:

monkey house 2009-01-01:16:54:00
monkey car 2009-01-01:17:01:00

Thank you.