As our 1st. Aussie to the forum, Welcome.
With regards to your question on saving the date, create a Macro for yourself called PUT or SAVE and use ~EP. Then add the item to your Fkeys ( I use F4). I suggest PUT because the / E P saves the date, description or amount.
When your talking about saving Many Invoices (ie: rents which are always the same) use the BLKCOPY and BLKPASTE.
Of course I assume you know that once you’ve saved a date, you then only the the portion you wished changed. For example you saved 13 May 2004. Tomorrow on the date column just enter 14 and press F4 to save 14 May 2004.