You can use three properties to describe the dates you would like to appear in bold. These are the same as those for the standard MonthCalendar and allow arbitrary dates, per-month dates and per-year dates. If you prefer to show the dates in a different way you can alter the OverrideBolded state information to achieve the required appearance.
Many accounting applications needs to show the week number alongside the dates to help the user correctly select the day of interest. Just like the standard MonthCalendar you can set the ShowWeekNumbers property as needed.