So that seems like they're doing some kind of math using the week of year in the calculation- but for what purpose? The UI doesn't seem to give you any options for day of week, just time of day.

Maybe there's code in there that checks day of week but it's hardcoded to run every day to make the UI simpler.

So maybe the service updates it's schedule weekly but the calculation ignores the year. This throws up an error at New Year's and borks the code that would reset when it's toggled on/off?