@Angstzaaier 

You can check time settings on Main Deco. Open its IP address in a browser, login with same password you have for Deco app, navigate in the Main Deco Web page to system settings. Example:

  @Alexandre. 
 

This is what I thought, but I can't get into the web interface. Are there other ways to access the webpage? I only can get the deco app to work so I was hoping to fit it there. I have tried the ip address of the deco, and I get the server doesn't respond. I also tried http://tplinkdeco.net but the same response from browser. I normally use deco in access point mode, and even tried to change to router mode to get more options, but the web interface doesn't seem to be there at all.

  @Angstzaaier 

I, too, have M9 Plus in my Deco mesh. It is my Main Deco. I shared screenshot from M9 Plus with you. I run Deco mesh in AP mode.

I may have an idea why you can't access M9 Plus Web interface. Your M9 Plus firmware version is very old. It is so old it comes without Web interface. It is also too old to be updated from Deco app. Please follow this document to update your M9 Plus firmware, use Method 3: How to Update the Firmware of Deco

You will only need to do that update with the tool once successfully. After you've updated M9 Plus to at least firmware 1.4, Deco app will gain ability to update M9 Plus and you will get access to M9 Plus Web interface through its IP address.

This old firmware is what may explain issues you see with your Deco mesh.

  @Angstzaaier 

I have now updated the firmware and finally have been able to access the web interface. It turns out it only seems to work via firefox. But the issue I had at first is still there. I have now updated firmware and checked time settings which are correct, but as soon as i connect any macbook to the deco network, the time and date are off by 2 months (oct 12, while date today is dec 18th). Even when i use pool.ntp or the standard apple setting for time, somehow if its connected to the deco network it is showing wrong time and date. while connected with any other networks or directly from the network router the time is correct, but as soon as i connect to tp link deco m9 it is incorrect. is there a setting somewhere which manipulates the data?

  @Angstzaaier 

Just to note, I can access M9 Plus Web interface using Microsoft Edge on Windows.

You have quite unusual issue. I don't work for TP-Link, but if I did, that would be my line of thought if I saw this escalated to me: 

If this is a bug in Deco, it continues for 3-4 years between Deco firmware 1.2 and 1.6. Yet, there are no escalations in regard to that problem from other people in about last 3 years I've been here. If it were such a glaring bug with Deco mesh, more than one person should have noticed it.

I can't tell what is wrong with your Deco mesh and overall setup. I could suggest you try these steps:

1. After connecting Macbook and it switching to wrong date/time, check in Main Deco Web interface it still has correct Continent/Ocean, Region, and Current Time;

2. In Main Deco Web interface change Region to incorrect, off by few hours from where you are, see if it changes anything on Macbook. You can restore Deco time settings to correct after that test;

3. As you do have network router, configure Deco mesh to run in Access Point mode. Whatever Deco settings impacting NTP might have impacted Macbook, they should go away with Deco mesh in AP mode. See Switching a Deco to Access Point (AP) Mode