Thank you so much for replying!

Yes, I spent a couple of hours yesterday trying to figure out if the answer was in there, and with the help of some friends I was able to find the solution - thank you!

For anyone searching this thread the precise chapter in MacroPod's tutorial is 'Calculate a date sequence' replacing the first two fields with the alternatives given 'to start from a date other than today'

To set the start date in the document, press CTRL-A, then F9, this will update all subsequent fields