This setting is replaced by 00030 - Show Which Day In Weekly as of version 2.17
|Show which day in weekly
|Defines, which day is shown in the Day Header Row when Calendar type [Weekly] is choosen.
|00005 - Calendar Type = [Weekly], 00019 - Show Header Rows must be enabled for minimum one day
If you choose a weekly calendar type (00005 - Calendar Type = [Weekly]) and you display in minimum one header row as day, then you can define, which day of the week should be shown in the header row. This is helpful, when your week starts on Sunday or you just want to show the Friday of every week.
Check the example settings and how it looks like for the same time range: