5 days can equal 7 days if you want it to

A story of misunderstood logic, if you can call it that.

So this morning, Bunda came to the house and gave us an envelope with an announcement of the 7 days ceremony for her aunt's death. She had spent all of Thursday night last week taking care of her aunt, so I assumed that the aunt had then, unfortunately passed away on Friday, later in the day. Bunda had been really tired and fell into a deep sleep and we sent her home to get some rest.

So when I saw the 7 day ceremony flyer, I assumed that the ceremony must be this coming Friday or later since, clearly, her aunt was still alive this time last week, until at least Friday. We were given the flyer as a way to ask for a contribution, which is normal and fine. I was just saying to Yeng that we should give Bunda Friday off and wondered how much cash we needed to give her. He then told me that the 7 day ceremony had been today.

I scratched my head, confused.

"But Bunda was taking care of her aunt on Thursday night..." I say.
"Yes," husband replies.
"So she was alive 7 days ago?" I continue.
"Yes. She died on Friday," the reply
"Um, so shouldn't the 7 day ceremony be on Friday then," say I, utterly dumbfounded.

And then, "they can choose when to hold the 7 day ceremony."

It was one of those I-don't-know-how-to-even-start-to-respond-to-that moments... Why call it a 7 day ceremony if it doesn't actually have to be 7 days after. Why a 7 day ceremony if it canbe 4 days or 9 days???

Anyone out there, reading this, if you are Khmer or have lived here for a long time and understand this, please help me to.