Time and Date Adjustment

LostKiwi

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I'm guessing because when done properly GPS is the second most accurate time source known (after atomic clocks) and is available all over the world unlike RDS.
 

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What is the GPS Week Number Rollover?

The GPS Week Number Rollover (WNRO) occurs every 19 years, with the next roll over taking place on 6 April 2019. Similar to odometers in older cars rolling over from 99,999 km to 0, the GPS WNRO is the resetting of the GPS calendar back to 0.

When the calendar resets, it can cause a miscommunication between GPS satellites and GPS receiver chips. As a result, some chips in satnavs will lose the ability to process certain functions.

What does this mean for you? It’s time to check your satnav. Depending on your device, you may need to update or upgrade.

Later cars get an update giving the hidden epoch adjustment menu, it might be something that can tweak for older cars
 

Botus

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So first time I've turned the key since DLS this spring....

both clocks wrong, both an hour slow. Date as has been for sometime, showing Aug 2019. Clicked day light saving option in region settings for UK, nothing changed. Adjusted clock on digital display - went straight to any time I set, analogue stays wrong. Key off key on no different. Tried various countries no change.

Worked out if I set to Belgium and untick day light saving that's GMT +1 hr left it at that - analogue stays wrong.

Parked up 45 mins later turned on the key, checked the date 7 April 2019 !!!
Astonished, checked the digital clock one hour out. Set to the correct time, analogue immediately span round an hour to match (but as has been for 3 years, remains 3 minutes behind). Checked date - its now jumped forward to Aug 2019 again. But clocks lined up and on correct hour, which is nice...
 
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While this issue is related to GPS week numbers, it's got nothing to do with the rollover or any pivot date.

As explained by @LostKiwi GPS uses 10 bit for the week number, which means it goes from week 0 to week 1023, i.e. 1024 weeks in total. Now what happened here is that the COMAND system wasn't prepared to handle 4-digit weeks: on Sun, Oct 21, 2018 the GPS week number increased from 999 to 1000 -> bollocks.

Now, since Sun, Apr 7, 2019, the 1024 weeks are up and we're back in week 0. Well, there was hope that the issue would thus resolve itself this week, but seems like it didn't. Maybe if week increases to 1 next Sunday it might work, as 0 can be a difficult number (anyone remembers not to divide by zero?). Or maybe the COMAND system was only programmed to handle 3-digit week numbers? Then we'd have to wait another 99 weeks from now. And even then, will it understand that we're 1024 weeks from the previous week 100 (which started Jul 22, 2001)? We can't really know. Depends entirely how the folks at Harman designed the software.

I think this is a rather annoying problem from bad software engineering which should warrant a recall even after warranty is up. It seems like all MBs with the COMAND system are affected.

@Botus clock is probably correct at the moment as both April and August are within DST range. Probably once internal date thinks it is Nov, time will again be off by 1 hour.

PS: one small addition: the new 13-bit week numbering is still pre-operational. I doubt there are any devices out there except some experimental setups which use the 13-bit. It's also a new channel/frequency as I understand, so it needs hardware adjustment as well.
 
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Botus

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Time only matches on each, if the cars is set NOT to use day light saving, hence I'm set at Belgium time zone.... when we last did GMT at the end of OCT clocks only aligned when you untick the use auto daylight saving, so whilst I'm sure all this is related I don't get how.... and with one clock lagging, it's almost as if one (digital) uses the satellites and one follows the lead of the other... but (the analogue one) has lost the plot by 3 mins when no extra noise is interfering with life (otherwise 57 minutes out)
 

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Mercs have a a 10 sec update when logging on to some cars.
 
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Mercedes have issued this in USA
 

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Botus

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thanks for the link Steve (interesting to see) and well done for using the correct post, there's a TIPS document in the UK too... and its a pile or garbage it does nothing at all to resolve the route cause... which is to do with GPS roll over....

Mercedes know full well that the epoch setting needs to be changed (which is dealer selectable, via a new secret user menu - after a software update [avail Dec 2018] on later cars). The reset may well help realign the two, but that can already be done without wiping your address or contacts...

the fix you can do without messing up your comand

Move comand settings to any CET region and ensure you don't tick daylight saving. When it next sees the right date, the two clocks will align (when back to GMT put it back to UK region and again don't tick day light saving).
To align the lag on the Analogue clock, be ready just before noon (or midnight if you're like that) and drop the power to the analogue clock and reconnect at it 12:00, it will spin to midday and match second for second the comand display

Only fun is where you have the later birds eye update in the summer when viewing the navigation time of arrival it will show one or two hours wrong (forget which, minutes are correct) with an L or something for local time.... but local to what I don't know …. GMT ?
 
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steve.link

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Also found this on an American forum - not tried it yet.

Correcting date/Time

Step 1 - Tonight before sleeping and letting your S go to sleep - switch off Command till the screen is completely off
Step 2 - First thing in the morning - you have a very small window ( approximately 60 seconds ) do the entire process as fast as you can , as its imperative to make the changes before the command syncs with the GPS Sats
Step 3 - Switch Key to position 1 or press start button once - till your ignition lights - light up in the dash .
Step 4 - Switch On Command - Navigate to the Date & Time Settings in the command - and quickly make the changes (took me 33 seconds)
Step 5 - At this point your time and Date should adjust - and you should be good to go
 
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steve.link

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thanks for the link Steve (interesting to see) and well done for using the correct post, there's a TIPS document in the UK too... and its a pile or garbage it does nothing at all to resolve the route cause... which is to do with GPS roll over....

Mercedes know full well that the epoch setting needs to be changed (which is dealer selectable, via a new secret user menu - after a software update [avail Dec 2018] on later cars). The reset may well help realign the two, but that can already be done without wiping your address or contacts...

the fix you can do without messing up your comand

Move comand settings to any CET region and ensure you don't tick daylight saving. When it next sees the right date, the two clocks will align (when back to GMT put it back to UK region and again don't tick day light saving).
To align the lag on the Analogue clock, be ready just before noon (or midnight if you're like that) and drop the power to the analogue clock and reconnect at it 12:00, it will spin to midday and match second for second the comand display

Only fun is where you have the later birds eye update in the summer when viewing the navigation time of arrival it will show one or two hours wrong (forget which, minutes are correct) with an L or something for local time.... but local to what I don't know …. GMT ?

Do you know the number/date of the UK TIPS Document? My Dealer says there isn't one?
 

Botus

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Do you know the number/date of the UK TIPS Document? My Dealer says there isn't one?

no, I was reading it at a UK garage on screen.

the USA post about how to adjust the clock just looks like a complicated version of mine, basically untick daylight saving, next time the car starts it looks for the satellites if a "corrupt one" doesn't jump in first the clocks will get it right and line up
 

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There's no such thing as a corrupt GPS satellite clock.
 

Botus

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There's no such thing as a corrupt GPS satellite clock.

I think you know what I mean.... if it finds an old one that's got muddled... versus a new one making sense
 

LostKiwi

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I think you know what I mean.... if it finds an old one that's got muddled... versus a new one making sense
I know what you're trying to say but others may not.
You mean an early one with a 17 year epoch as opposed to the later ones with a near 80 year epoch.
 
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steve.link

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Mercedes have issued this in USA
Took this TIPS document to my Merc Dealer today and they have set my clock to the exact correct time (it always lagged by 7 minutes previously) The date is still about 5 months ahead in November sometime but I can live with this. The best bit was they did it for free!
 

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…. small update for clock reset.

I had another gremlin in my car that had been bugging me for 3 months, (Radio / other sources not muting for Nav instructions) oddly it disappeared on the way to a specialist and "as it was fixed" we only took a cursory glance to see if it was diagnostic kit adjustable - as they believed it was - but we didn't find it. As usual with faults it was magically back on the drive home. The two argue at the same volume and you understand neither.

Source muting working, was a week after clearing an error message for the CAN bus throwing it's teddies. So we spoke about if it happened again would a battery reset help and had a laugh about the silly procedure Merc have for doing the clock whilst re reading the UK TIPS document for the 221. It finishes up saying you can't set the date any longer (even at a merc dealer).

So with my analogue clock lagging 5 minutes and the source muting bug back.... I thought I give the battery reset idea a go last week. Open the boot lift the spare wheel cover and in-line with the wheel centre on the right is an earth strap with a 13mm bolt. No sparks, no issues, no drama, (having unlocked the doors or the alarm siren keeps sounding) unbolt it. Lift for a few seconds to do the clock or 10 mins to battery reset modules.... push it against the body, wind in the bolt and tighten whilst holding good contact on the strap to the body, job done. (Might need to play with the windows not checked)

What you get is the clock spins to 12 and the comand gets the time right (how?) but the date is very wrong. I was hoping it might find a new satellite and reset the analogue clock for me but in the three times I tried, Sat around 11:00, Sun 08:00 and during a longish drive and today at 11:57, each time the date was some random point in 2003 !!! and hasn't moved since.

Having been typing rubbish on forums all day I forgot I could get it right by doing it again at midday and with three seconds to spare I got the strap off and reconnected bang on 12:00. Now the analogue clock is spot on to the second for the first time in 4 years. And its an easy fix you can do at home in 30 seconds start to finish... no need to waste 6 hours in a round trip wondering if a Merc dealer is going to ask you £200 quid to do it by some mental process that wastes everyone's time and needs doing every 6 months...

The date bit I find very intriguing… since the impact many are seeing as we got towards or entered the current satellite epoch (19 years of fun starting 6 April 2019), the date has been either correct (randomly a few times each month) or displaying 6 months off from the correct date (usually from 6 months past, but once I got 6 months in front). Now its stuck in 2003 and not moving.
 
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Botus

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W221 and W216 time and date issues are because the car can no longer correctly understand the signals coming from satellites after a 19 year epoch ended.

There is no manual override or ability to stop it looking automatically for these satellite signals. It can not be fixed (a software update Mercedes can't be bothered to support is required).

There is a complex Mercedes dealer time wasting work around, its totally unnecessary and almost pointless. It needs doing each time the analogue clock gets muddled or out of sync (and I believe at every daylight saving change).

The date from now on will always be incorrect and un-adjustable (even when you waste your life at the dealership).
The digital clock also no longer supports automatic changes for day light saving.

For BST
In comand go to change the time zone, select a central European country and ensure you untick daylight saving

For GMT
In comand go to change the time zone, select UK and ensure you untick daylight saving

the digital clock will be correct at the next cold start of the vehicle, the date will be garbage, the sat nav during the summer will show time of arrival an hour early, traffic updates work normally

if the analogue clock has slipped back (1 min a year on ave) and or is an hour out and won't get over itself. At 11:57 unlock the car and open the boot. Lift the spare wheel cover and in-line with the wheel centre on the right side of the wheel well is an earth strap with a 13mm bolt. Undo this bolt (No sparks, no issues, no drama). Lift for a few seconds and at 11:59.58 seconds push it against the body and wind in the bolt and tighten (whilst maintaining good contact of the strap to the body). As you reconnect the power the clock spins to 12:00

job done
 
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