It might be worth adding a link here to Robert Odom's paper 'Vettius Valens and the Planetary Week' which is available online:

https://digitalcommons.andrews.edu/cgi/ ... ntext=auss

Touching on the point made about whether there is universal agreement on the day being Friday or Sunday, etc, what Valens shows is that the technique of planetary days and hours rests on local society expectations. If your society is calling it Sunday and doing what society does on a Sunday, then it’s Sunday. If extra days are added to the calendar, that starts to count again because a new epoch has begun. (Note Valens 1.5, where he explains the formula for finding the day of the week from the epoch of Augustus, giving references to intercalations to show he was using the reformed calendar in his calculation of days, before he goes on to explain the calculation and rulership scheme of the planetary hours.)
Keep in mind that although Valens explains their symbolic planetary rulers, his work shows reliance on the temporal planetary hours as a calculation technique to identify other points in the chart (eg, I.5) - so there was more of a technical reliance on these time divisions in his era than most astrologers are used to today.

Thanks for the link, Deb!

I red the paper quickly but could not find that he writes that a new epoch was begun when adding days. Maybe the conception that the names of weekdays are just a social agreement is right but I am not convinced because again and again I saw that the importance of the lord of the hour in horaries.