How can I define a date?

I find a great number of functions to add, subtract, decypher and do other stuff with dates.
But I cannot find any way to simply define a date myself.

I'm in need of calculating for 40.000 records an amount of revenue, based on how long a contract is already running. I want to calculate it till end of the previous quarter.
I wanted to do this quickly for now & do fundamental work later.

So my line of thought was:

  • define custom col #1: EndOfQuarter, i.e. 31 March 2024 (this is my issue yet)
  • define custom col #2: dateDiff ( [EndOfQuarter] , [ContractStart] , "month" ) * MonthlyRent calculate the running amount of rent due

So how do I define some date?
And if this line of thining wouldn't work at all, what would be a doable alternative?

I should have posted this in "Get help".
I've made a copy myself already, so please delete this Bug report entry.