@Gertrude ***********
you can go upto 30 days before expiry so the 29th is fine.
However, regardless of what day or date you are going I would recommend going a day or two before to get the paperwork.
The day you are going for the extension, arriving at IT Square at around 8am going straight upto immigration and standing at the first counter 1 (back wall where the paperwork is) is the quickest way to get it done if you want to be in and out within 30min-1hr. Otherwise you will be spending 2-4 hours there just waiting to be seen and getting your passport back.