Hi I'm just filling in the form to apply for a single re entry visa

The form asks for the date of departure  and the date of return.

Does anyone know if these dates have to be exact,  and  fixed as I may decide to return early 

They don't have to exact. The re-entry permit will be good for you to return anytime on or before the date your current permission to stay expires.

23 minutes ago, elviajero said:

They don't have to exact. The re-entry permit will be good for you to return anytime on or before the date your current permission to stay expires.

How about if I get a flight out earlier after I have obtained the re entry visa date I leave

4 hours ago, salavan said:

How about if I get a flight out earlier after I have obtained the re entry visa date I leave

The re-entry permit runs from the date it is issued until the expiry of your permission to stay. (If it is a single re-entry permit, it is obviously dead once used for re-entry.) I suspect the dates on the form are to allow immigration to detect if you are being an idiot. Some assume a re-entry permit stops the clock on their permission to stay, and that they can return far in the future to restart the clock. Anyway, the dates you specify on the form are of no consequence as far as the validity of the re-entry permit is concerned.

4 hours ago, salavan said:

How about if I get a flight out earlier after I have obtained the re entry visa date I leave

No problem.

 

The dates really aren't important. I usually leave them blank.