In reunion, you can create a calendar list of certain events. Simply select "List" from the file menu, and then chose "Calendar..." From here, decide which event you'd like to list: births, deaths, marriages, emigrations, censuses, etc. It does not appear that all events can me made into one calendar list. Next, designate the time span the the folks that you want showing up (all, marked, living). Once the list is created, columns can be added or removed. For example, I can add an age column. Finally, decide the output of the file: text or web file. The file will be a list only and is not available in a "wall calendar" format.
To the left I have an image of the birthday calendar list as it appears in reunion, before being sent to a file. Those with January birthdays with no specific date are listed first, followed by a chronological list of everyone else.
I see that today there are four birthdays in my family tree. The "closest" relative is my half-brother's Great-Grandmother, Evie Williams Belk. Yesterday was my Great-Grandmother's birthday.