DE EN ISO 8601 and its local German predecessors define a calendar week, Kalenderwoche, as a specific seven-day span in a certain year. Since the 1970s at least, the calendar week is understood as starting on Monday and the first one having the majority of it days in January, i.e. at least Thursday through Sunday. They are used more prominently than months in several fields and businesses.
However, it seems hard to find out exactly how people usually refer to a specific week beyond relative terms like letzte / diese / nächste Woche. One common way is using the abbreviation KW for Kalenderwoche followed by the ordinal number of the week in the year, e.g. "Wir machen das in KW 11". There are at least four ways to specify a certain week (using Unicode / CLDR terms from TR 35):
weekOfYear: ordinal 01 through 52 or 53, e.g. "KW 42" or "in der 31. Woche"
weekOfMonth: ordinal 1 through 4 or 5, e.g. "zweite Aprilwoche" or "3. Woche im Juni", but also counting backwards, e.g. "letzte Januarwoche" or "vorletzte Woche im Mai"; note that this is only covered implicitly by the applicable local and international standards
weekOfDate: a week specified by an anchor date, given by the month and the day of the month, e.g. "die Woche des 26. September" or "die Woche um den 4. Dezember" but also "die Weihnachtswoche" or "die Karwoche", where the day of the week of the anchor date may either be arbitrary (i.e. any from Monday through Sunday) or be limited usually to either the first or the last day of the week (i.e. mostly Monday or Sunday)
weekOfInterval: a week specified by its start date and its end date, both given by the month and the day of the month, e.g. "die Woche vom 2. bis 8. Februar" or "die Woche vom 27. Juli bis zum 2. August"
How frequently are these variants being used in predominantly German speaking areas? Is there any regional difference (e.g. between Northern Germany and Austria) or are conventions established in a specific field (e.g. academic administration) more important?
I would like empirical evidence, not just anecdotal evidence, because I'm trying to get the CLDR data changed. This data, which is used a lot for software translation and localisation, currently lists German as preferring
weekOfInterval, while not considering
weekOfYear being used at all (which is definitely wrong). This is also why I'm asking in English and would prefer answers in English.
PS: Is "1. Adventswoche" the week that ends with the first Advent Sunday or the week that starts after it? (The Christian Churches usually start their weeks with Sunday.)