Just finished a 3 night stay. System is crediting me 2 nights, this is like the 3rd time this has happened this year. It's wonderful that I get to spend so much time on the phone with Marriott to correct their mistakes. Odd that they never happen in my favor...

Received confirmation email at time of booking with the correct dates, another email 5 days before checkin (again with correct dates) after booking on the marriott.com website. Now on the phone arguing with them as they're trying to tell me it was booked through kayak (untrue) and that's why their system shows the wrong # of nights? Pathetic.

Do you have your bill/folio? What does that say

Normal check in and checkout times? The only times I had a problem (so far) is if I arrive past midnight or checkout before midnight. For after midnight arrival, they need to go in and adjust the arrival time in the system to 11:59pm. For departures before midnight, I don’t checkout until after I leave.

+1 That's the only time it happens.
Look at your folio - There is no way for them to mess this up unless you arrive past mid night

I've checked in after midnight at least 5 times this year and there were no issues. Although I always mobile check in, so even though that doesnt truly do a check in, it likely alerts to hotel so when they ready the room and keys, it is before midnight.

that's the way to do it to avoid the problem the OP is likely posting about. Post midnight arrivals somehow mess up the night count unless you check in online before you arrive.

It can be fixed via Marriott customer care, but it is a bit of a pain.

Online checkin does not check you in. I have done this and still required several communications to get my nights fixed after a 4.30 am arrival.

This is a totally made up excuse (not uncommon these days). If your booking was through Kayak then NO credit would be due not just some of the nights. Reps need to be called on this and forced to do the research to find out what is happening and not just make things up to get you to go away.

As for number of nights, it does seem there are more and more issues with late check-ins and early check-outs. It's not really a system problem as it is merely doing simple date math and if you do/don't cross midnight then a day or tow off is technically the right answer. Howere, what is missing, in my view, is proper training to the property staff to adjust the dates based upon the situation. Some properties are better at this than others. Programmatically, they could add/subtract 12 hours before computing the dates, but MR IT is not going to catch that, or care. It's not up to them to fix the mistakes. Put them on the front line for a day/week, my guess hope is you might see great improvement.

Bill shows the three nights and the payment.

Yup, checkin around 3-4pm, checkout like 7am.

Yea, I didn't check in or out in the middle of the night AND like I said the system generated a confirmation email at booking and 5 days before checkin with the same confirmation # and the proper # of nights. No idea what is going on with the system. The agent said she called the hotel and they confirmed the # of nights and had it in properly on their end. The agent said wait 10 days and check but it "should" post properly even though marriott.com thinks it was two. My guess is in 10 days I will be on the phone with them again...

I'd file a missing stay request and send the folio. then call back. This should be straightforward then?

I also had a stay post with only 2 of the 3 nights. My JW Marriott Venice, post 10 days after check out with only 2 of the 3 nights posting originally. I checked in around 3 pm on the 7th and out around noon on 10th. After lodging a complaint, once again, I received the credit of all three nights a week later.

Every single legacy SPG stay, 3 x Westins, 1 Lux Collection, 1 Sheraton, 1 St Regis have all posted correctly the day after check out.
Every single legacy Marriott has taken at least 10 days to post, one is currently at 12 days, and there have been errors in half of them that's had to have a case filed

Staying at JW Marriott in China at the moment, 4 nights stay. On the third day (today) I noticed on the app (same on the webpage) that details of my stay changed, i.e. it now shows that my stay is 3 nights and that we arrived on Tuesday (but in fact we checked in on Monday, 1pm)... ...?? The only thing unchanged on the app is the final price. I will see tomorrow upon check-out what will final folio say... I am not paying for the first night if they intend to steal it from me...