When/where for dates

In the following sentence, should I use ‘when’ or ‘where’ to refer to a point in time?
"... it should be calculated by the exchange rate listed in... on the date [where/when] the contract was executed"

I got confused, because I’ve found ‘when’ and ‘where’, used for similar structures in the literature; e.g.
- “...effective from the date where the investing entity acquires joint control...”
- “...It marks the date when Allah appeared to Ibrahim in a dream...”

Thank you,