It will show both Julian and Gregorian dates.
Technically, are these not the same?
...And merely differ in which 'day' they fall on in our civil calendar.
Oh my, I hear Keble coming now...
Why not just show both dates at the top of our pages where we show 'Today's date' now?
Demetri, who celebrates his nameday (Oct 26) twice - on each calendar - a true ecumenist!