DST issues with WxSim WxSimate (ECMWF Mix) and WxSim-Lite

Ok, so not sure if I posted about this in a thread recently that was not relevant or not.
However, this year when I transitioned through to DST, I thought all was good.
However it was not, WxSim/WxSimate/and WxSim-Lite did not auto adjust.
I found this out by chance when forecasts started showing way outside (temp (+/-) 2 degree C).
I fixed it by manually checking all the in DST check boxes, and it ran good for weeks, until recently I noticed similar issues and investigation resulted in finding that the WxSimate (ECMWF Mix) was not selected for DST, I mean open the WxSimate (ECMWF Mix) and within there is a checkbox for use DST.
@Tom_Ehrensperger Tom is there any info on how all the different programs deal with DST.

You can see the results of DST not being taken into account (example 1hour Out) by viewing the change in my (errdep) and (errdate) historic images, note we changed to DST on 2023-10-01 02:00:00 for reference. https://beaumaris-weather.com/data/wxsimerrimages/
Kindest Regards,

Tony I know that WXSimLite has DST settings where you have to tell it when to make the change. I’ve already adjusted mine for this change and next March.

We are about to change back to GMT this weekend so I’ll take a close look at what happens.


Had not noticed the ECMWF mix had a dst so that will be 4 that need changing on Sunday manually
Wxsim, Wxsimate, ECMWF Mix and Wret I don’t use lite

It would be good if all the WxSim programs could be switched by changing the setting in just one of them because they all change at the same time or at least I can’t think of a reason for some programs to be using DST whilst others aren’t?

Perhaps this is something we could ask Tom to add?

I seem to remember if I change one (not Lite) it asks if I want to change all but not sure which one that was. I think Lite has that setting because it needs to switch DST off/on during some runs when scanning files.

I agree that setting needs to be somewhere as not everywhere changes on the same day. It either needs picking up from the operating system or have a setting in WXSim like Lite which sets all the others on the appropriate date.

I’d completely forgotten to change euromix so I’ve been running all year on GMT in that :scream:


The last DST changes Tom made I think where outlined here : New beta version to try!

that sounds about right and I do not think Tom got it resolved for other areas which use different dates and days in month , I’ve had to do the manual update of DST since then

Yes that is correct Stuart, and it did seem to work, though not for the last Off DST or On DST for me anyway.
Yes I think you could be right there Harold.

I only mention this other one also, as only myself and Harold @hcorrin commented on it back in September. Not to do with DST, but ensuring ECMWF mix is actually being used in WxSim.

1: the correct naming of both wdata.txt and wdatamixed.txt

2: the correct file to be used in WxSim Data Import

Another possibly missed step by some, could be these 2 points : Some things to check

Kindest Regards,

Hopefully I can clear some of this up!

I tried pretty hard to make the DST switchover automatic, but it seems (as best I can tell) that there are differences (perhaps due to different Windows international settings) that made this work for some users/systems and not others. Actually, I tried to make this in the form of a message alerting the user to make the change. Unfortunately, this did not always work, and (worse) I believe I recall it “going off” as a false alarm, so that I made an option to simply turn off the alert system.

SO, the bottom line is yiou have to do it yourself. IF you do it in WXSIM, you should be prompted for whether you also want the changes made in WXSIMATE and WRET. In any case, when the time change comes, just make sure all three programs have the proper setting (each has a check box for that).

WXSIM-Lite is a different matter. There, you should NOT try to change the DST setting, but rather simply enter the start end dates, under the menu item of that name at the top. The reason is that it’s not the current day that matters, but rather the day it was when the forecast being analyuzed was made, and the analysis period often straddles the changeover date. Just set those dates and leave that alone until the next year.

Yes, be careful with the namking of the data files. I’ve seen some users’ initialization files not having this right. WXSIMATE should be set to create wdata.txt,as in the past, but if you’re using euromix, you need to tell WXSIM to import wdatamixed.txt. In euromix itself, the file to import should be wdata.txt, and to export it should be wdatamixed.txt.

As far as the DST setting in euromix, that actually is relevant only for its display. That won’t affect the other programs.

I hope that helps!


Hi Tom @Tom_Ehrensperger ,
Thank you for the detailed explanation. Greatly Appreciated.
I have many questions regards this detail, though not able to apply time currently to question them.
I will do so in the next day or so.
Kindest Regards,

Could you make it that if you change it in WXSIMATE that it also prompts to change the others. When running manually I visit WxSimate first, and would change the setting there meaning I don’t get the prompt and have to change the others manually.

It’s good to know that Euromix only uses the setting for display purposes, so it’s not a problem if we forget to change that, but as it is a concern when you forget to change it, then months later discover it’s wrong (and forget it’s only for display purposes) could it be made to follow the WxSim setting?

Changing wxsim to non dst this morning failed to change the others no warning messages so all had to be done manually, I know it used to do it about 3 years ago but lots of updates since then

Yes I found the same here this morning. I’d suggest that Tom adds an option for the DST dates to WXSim identical to the one in WXSimLite where once per year we change the dates, WXSim could then create a file which all the other programs can read. It’s no good using WSXimLite to do it as not everyone uses that!


I think the time and date should be taken from the computer. Then there is no need to change anything

Computer time would normally be local time and a lot of data, e.g. GFS, etc is provided in UTC. So there needs to be a conversion between local time and UTC for the data to be in sync and any times that are output are correct.

It can become even more complicated. I’m running WxSim on a virtual PC in another country. My local time is GMT/BST (UTC/UTC+1). The virtual PC is in Finland which is UTC+2/UTC+3. However, you can’t set the time on a virtual PC, so it takes server time, which is always UTC. Without a way to set the DST manually there would be no way for me to make WxSim calculate with the correct time!

Yes but WXSimLite still needs to know when the changes happen as it reads log files and has to make sense of which data is DST and which is not. Not sure how it would work if the computer was running UTC (or GMT in my case :wink: ) either which might mess up stuff.