As Google hasn't introduced a simple copy/paste option in its Calendar which would be indeed a quite useful feature, here's what you can do instead:
If you need to duplicate an event and you dont want to write its long name /description in the boxes just select
More actions/Duplicate event
Pick the date you want and click Save.
The event is now copied to a new day.
In the case you need to create multiple such events in your calendar a copy paste option would be actually quite useful, as you don't want to repeat this previous procedure N-times.
However, if the event is recurring on a regular basis here's what you can do:
Then select how often the event will be repeated, e.g. once per week, or per 2 weeks...
Select when the event starts and when it ends, or you can specify the number of occurrences of the event.
Still the simple copy/paste function would be great, Google!