<<< macOS WeeWX Guides >>>
Managing The Change to Summer Time WeeWX 3.5 and Above
When the clocks go forward to Summertime there may be an issue with the time synchronisation between the Davis VantageVue and Weewx. This issue presents itself as the website being locked at 02:00 and if you are sending reports to other organisations they will probably be mailing you to let you know that synchronisation has stopped.
This issue is explored in a lot more detail on the User Forum, but suffice to say that there is a simple fix to the issue.
The problem is as follows. Because the vantage logger has neither UTC time stamps nor DST flags it can't make a distiction between a time stamp in wintertime and in summertime.
The vantage driver hast to convert the logger time stamp to UTC and makes an assumption about being summertime or not. This will be based upon the server time stamp and DST flag
At the start of a new archive interval the vantage driver asks the logger for all records newer than its last registrated record in the database. Because of the miscommunication summer-wintertime time stamps the logger thinks it has no such record in its database and offers the vantage driver all records starting with the eldest record. (Note: the logger thinks the vantage driver asks for time stamps 01:00, 01:05, which are not in the loggers memory because it has instead time stamps of 02:00, 02:05 etc)
On its turn the vantage driver takes a conclusion that no record has to be retrieved and no record is stored in the WeeWX database.
The next archive period the same story starts all over. This will repeat until all logger data will be overwritten (this will take 4 days with 5-minute registrations).
The following solutions have been found so far:
- Dump all logger data to the WeeWX database
- Clear the logger memory
- Wait until the logger memory has overwritten all data with time stamps before start summertime
- Don't let the vantage driver store the logger data between start summertime and start summertime + 3600 s
- NOT Tested and NOT Reccommended Change the time stamp of the newest WeeWX record to time stamp+3600
Thanks to Luc Heijst for the explanation
I use the Dump All Logger Data option as this continues processing with no loss of data, by forcing a full dump from the VantageVue which will effectvely synchronise the clocks, then everything will progress as before.
The commands for this are as follows and are based on running WeeWX as a Daemon on the Mac OS as detailed here
First you have to log into the directory that contains your WeeWX website, in my case this is in my Groups directory tree
$ cd /Groups/revitt/WebSites/Weewx/
$ sudo launchctl unload /Library/LaunchDaemons/com.weewx.weewxd.plist
$ /Groups/revitt/WebSites/Weewx/bin/wee_device /Groups/revitt/WebSites/Weewx/weewx.conf --dump
Using configuration file /Groups/revitt/WebSites/Weewx/weewx.conf
Using Vantage driver version 3.0.7 (weewx.drivers.vantage)
Proceeding will dump all data in the logger.
Are you sure you want to proceed (y/n)? y
Starting dump ...
Records processed: 2560; Timestamp: 2017-03-22 07:20:00 GMT (1490167200)
Finished dump. 2560 records added
$ sudo launchctl load /Library/LaunchDaemons/com.weewx.weewxd.plist
Then when you log onto your website you should see the updated data